How to read this pattern?

#1

I am trying to make a pair of socks for the first time and I am a bit confused about this part of the pattern.

This is at the turning of the heal

row 1 (ws) Slip 1, P__, P2tog, P1 turn back to rs

I dont know what they mean by the P__

TIA,
Shannon

#2

The blank space is probably for the number of stitches in your size, but without the pattern, ???