With 120 stitches on my needle, I'm instructed to PO (8), [P2TOG,P4) 17 times P2TOG, PO (8) and the. I should have 102 stitches on my needle. Help!
So, sorry but I don't really understand the question.
You have 120 stitches, you do 18 decreases across the row (17 P2tog, P4 plus one extra P2tog). 120 - 18 = 102.
Try the row instructions in plain english:
Purl 8 stitches, *purl 2 tog, purl 4 stitches. Repeat from * 17 times. Purl 2 together, purl to end of row.
Hope this helps.