How many chain crochet stitches to make 88?

To make 88 single crochets, you would make 89 chain stitches and go into the second chain from hook to make your first single crochet.

To make 88 double crochets, you would make 90 chain stitches and go into the 4th chain from hook. The first 3 skipped chains count as a stitch which is why you are ending up with only 2 less than the original chain.