> however numbering the bond 1 means there's ambiguity between it being between 1 and 2 and between 1 and 6

It might *appear* to you all of a sudden that there's an ambiguity, but actually there's none. Look at these two molecules carefully:

[![enter image description here][1]][1]

Note that the numbering for the molecule on the **left** will increase in the **anticlockwise** direction, while the numbering for the molecule on the **right** will increase in the **clockwise** direction. The **pi bond in each case gets the number $1$** (and it should, because both the molecules are identical)

You seem to be assuming that the numbering for the molecule on the left *also* applies on the molecule on the right. But, that is not the case, as shown above.

  [1]: https://i.sstatic.net/FkTSo.png