Ch as a st?

[GingerSnap713]

I have a pattern that has a whole row consisting of the pattern: 1dc in each of next 2dc, ch1, skip ch1 space. The next row says to sl st in the first 7 st. Would this count the chains as well? Or just the dc? I'm not sure if I'm supposed to skip the chain stitches I made in that row. The pattern is a baby dress and the 7 sl st is to start shaping the arm holes.

[Granny Square]

Welcome to the 'ville.  I would interpret that this means to stitch into chain spaces too.  A big clue was 'shaping the arm holes',  if you skipped the chains it would pucker a tiny bit and make the armholes smaller, which wouldn't make sense; you want armholes to be roomy and lie flat.

When I have to slip stitch or regular stitch into a chain, I typically don't insert the hook under the top 2 loops of the stitch as you would for a SC or taller.  For slip stitches into foundation chains I use the back loop of the chain (not the back bump; it's the top loop with the chain facing you) , for regular stitches into a chain (like when you reach the end of the row and make the last stitch into the turning chain of the row below), I use the back loop and the back bump - it's just easier IMO than working under the top 2 loops of a chain.