This totally makes sense and I think I have been adding stitches - I have been working on more hats which I think I have mastered in regards to that they aren't coming out to big or too small ( I use either do them in continuous spirals or if DC I don't count my turning chain as . I haven't made any scarfs and I was working on a blanket but I was not within the pattern and I was either short stitches or add more stitches and then I was adjusting so it wasn't too terrible.Does it instruct you to chain one or two stitches at the end of the row? My guess is that is the "turning chain" they are referring to.
Normally the chain stitches you add at the end of the row count as the first stitch on the second row, and will keep your borders straight and stitch count even. Normally you only stitch into these at the end of the next row (just before you turn around, you'll stitch into the last-- or first, whatever-- stitch of this chain, and the others replace the "post" on a normal stitch.)
If so, you'd normally chain 2-3 stitches (depending on if you are using sc or dc, tc, etc.) at the end of the row, and then if your borders are supposed to be straight, you stitch into the *2nd* stitch of the previous row, not the first. The chain stitches stack up on top of the last row's final stitch and when complete will make a neat edge and keep you from adding or subtracting stitches on accident/ Depending on the pattern, they might want you to stitch into one of the chain stitches you just made, especially if you are increasing on the edge rather than in the body of the work.
Am I, like, totally confusing you now? Sorry. No work for me in the crochet technical writing world.