What does this mean?

the pattern says:

(P7 (-:9), P2tog) 4 times, P1. 33 sts.

i’m currently doing a stockinette stitch with 37 sts. (it’s a hat)
i’m not sure what the (-:9) means


i guess i shouldn’t have had a glass of wine while reading a pattern!

i just got it… sorry!

what does it mean ? :shrug: Is it for the size?

…while decreasing the instructions said

for small & large only!
so the inner parenthesis was

  • for the medium
    and :9 for the large.

sometimes i think i make the pattern way more complicated than they already are!