Shaded stripes reversible throw

[crochetgrammy]

Working behind ch1 space

[Granny Square]

Welcome to the 'ville!

This is an educated guess based on situations I've run into before. A chain space often skips a stitch in the row below.  

I'm guessing row 10 said something like 'sc, chain 1, skip next stitch, etc.  (note, the stitch you skipped would have been in the prior row, which is row 9)

Now you are in row 11, and it says, for example, " working behind ch1 space, (which is in row 10), sc in sc (which is from row 9).

If row 11 is a right side row, this will leave the chain showing on the right  side, and will be slightly raised because of the stitch behind it.  This might be a decorative 'bump', or it could possibly be used as the base for a decorative stitch made over the surface of the right side of the fabric - I've encountered this on lace items.

The 'working behind' part is a little bit of a odd move - normally you stick the hook into a stitch from front to back.  Here, you  will be doing so from the back to front, under the chain, then turn the hook to point to the back again to finish the stitch.  It sounds more complicated than it is.

One way to check, is there something on the surface 'going on' at that spot on the pattern photo? A decorative bump, or a stitch made across the surface of the fabric landing at that spot?

 

[Granny Square]

Just looked at what this pattern was supposed to look like, and found that there was errata published, and appears to be on the row you quoted - it's missing an asterisk.

https://www.crochetmagazine.com/corrections/pdfs/M22120_Errata.pdf

[bgs]

So are we using this technique? If so read under header Double Crochet in Back (dcib) or Back Stitch

[Granny Square]

This doesn't appear to be interlocking, I've worked in that style, from a book I have by the designer you linked.  Galik's interlocking patterns (that I'm aware of) use US DC, the OP's pattern uses SC (at least in the line involved in the errata).

The OP's pattern looks like this, and appears more solid.