It's all part of reading patterns. We've all had similar questions before so you're in good company.
8th row: Rib6,rib2 tog,(rib6,rib2tog)15 times,rib5. 117sts
Start the row by ribbing 6sts, then rib 2tog. Next rib6, rib 2tog and repeat this sequence of sts 15 times total. So rib6, rib2tog, rib6, rib2tog, rib6, rib2tog etc. Finish the row with rib5sts.
This is likely to space out decreases from the rib pattern to the main body of the sweater. If so, it's not so critical that the numbers be perfect, simple get in the decrease of 16sts across the row.