My book says the number of outermost electrons in silicon is $4$. Yes, right. But then it says those are $\mathrm{2s \ and \ 2p}$ electrons. Electronic configuration of silicon is

$\mathrm{1s^2 \ 2s^2 \ 2p^6 \ 3s^2 \ 3p^2}$

So How the outermost electrons are $\mathrm{2s \ and \ 2p}$ electrons. Those belong to $\mathrm{3^{rd}}$ Shell.

Then it says the maximum number of electrons in the outermost shell is $8$. Correct. But then it says those are $\mathrm{2s+6p}$ electrons. How?

I'm actually studying physics and i hate chemistry. I don't know much about electronic configurations and all. But i have to know in order to go any further. So please give me a suitable answer.