My book (NCERT- Chemistry Part for class 12) Coordination Compounds-NCERT (Page-2)
Mentions the following statements as a postulate of Werner's theory:

The primary valences are normally ionisable and are satisfied by negative ions.

I get that the primary valences basically mean the Oxidation Number of the central metal atom in the coordination sphere. And they are ionisable as the ions that are outside the coordination sphere get dissociated in aqueous solutions.
But I don't get how they are satisfied by negative ions only?

For example, in $\ce{[Co(NH3)6]Cl3}$ . It is clear that three Chloride ions satisfy the primary valence(+3 oxidation state) of $\ce{Co^{3+}}$ .

But if we consider $\ce{K4[Fe(CN)6]}$ there are no negative ions outside the coordination sphere.
So here are my doubts regarding this

1. Do the Potassium ions satisfy the primary valence/oxidation state of Iron here? Which means the book is wrong?
2. If not, then are the Cyanide ions satisfying the primary valence of Iron? If yes, then we can say Ligands can satisfy both Primary and Secondary valences at the same time? (As cyanide ions are already contributing to coordination number(secondary valence))
   But I don't feel this could be true since that contradicts the fact that primary valences are ionisable.

My book (NCERT- Chemistry Part for class 12) Coordination Compounds-NCERT (Page-2)
Mentions the following statements as a postulate of Werner's theory:

The primary valences are normally ionisable and are satisfied by negative ions.

I get that the primary valences basically mean the Oxidation Number of the central metal atom in the coordination sphere. And they are ionisable as the ions that are outside the coordination sphere get dissociated in aqueous solutions.
But is it necessary that Primary Valencies are satisfied only by negative ions?

For example, in $\ce{[Co(NH3)6]Cl3}$ . It is clear that three Chloride ions satisfy the primary valence(+3 oxidation state) of $\ce{Co^{3+}}$ .

But if we consider $\ce{K4[Fe(CN)6]}$ there are no negative ions outside the coordination sphere.
So here are my doubts regarding this

1. Do the Potassium ions satisfy the primary valence/oxidation state of Iron here? Which means the book is wrong?
2. If not, then are the Cyanide ions satisfying the primary valence of Iron? If yes, then we can say Ligands can satisfy both Primary and Secondary valences at the same time? (As cyanide ions are already contributing to coordination number(secondary valence))
   But I don't feel this could be true since that contradicts the fact that primary valences are ionisable.

My book (NCERT- Chemistry Part for class 12) Coordination Compounds-NCERT (Page-2)
Mentions the following statements as a postulate of Werner's theory:

The primary valences are normally ionisable and are satisfied by negative ions.

I get that the primary valences basically mean the Oxidation Number of the central metal atom in the coordination sphere. And they are ionisable as the ions that are outside the coordination sphere get dissociated in aqueous solutions.
But I don't get how they are satisfied by negative ions only?

For example, in $\ce{[Co(NH3)6]Cl3}$ . It is clear that three Chloride ions satisfy the primary valence(+3 oxidation state) of $\ce{Co^{3+}}$ .

But if we consider $\ce{K4[Fe(CN)6]}$ there are no negative ions outside the coordination sphere.
So here are my doubts regarding this

1. Do the Potassium ions satisfy the primary valence/oxidation state of Iron here? Which means the book is wrong?
2. If not, then are the Cyanide ions satisfying the primary valence of Iron? If yes, then we can say Ligands can satisfy both Primary and Secondary valences at the same time? (As cyanide ions are already contributing to coordination number(secondary valence))
   Also, that contradicts the fact that primary valences are ionisable.

My book (NCERT- Chemistry Part for class 12) Coordination Compounds-NCERT (Page-2)
Mentions the following statements as a postulate of Werner's theory:

The primary valences are normally ionisable and are satisfied by negative ions.

I get that the primary valences basically mean the Oxidation Number of the central metal atom in the coordination sphere. And they are ionisable as the ions that are outside the coordination sphere get dissociated in aqueous solutions.
But I don't get how they are satisfied by negative ions only?

For example, in $\ce{[Co(NH3)6]Cl3}$ . It is clear that three Chloride ions satisfy the primary valence(+3 oxidation state) of $\ce{Co^{3+}}$ .

But if we consider $\ce{K4[Fe(CN)6]}$ there are no negative ions outside the coordination sphere.
So here are my doubts regarding this

1. Do the Potassium ions satisfy the primary valence/oxidation state of Iron here? Which means the book is wrong?
2. If not, then are the Cyanide ions satisfying the primary valence of Iron? If yes, then we can say Ligands can satisfy both Primary and Secondary valences at the same time? (As cyanide ions are already contributing to coordination number(secondary valence))
   But I don't feel this could be true since that contradicts the fact that primary valences are ionisable.