Understanding instructions

I’m making my first garment and I’m not sure I understand the instructions, what better place to come than all you wonderful knitters. Ok so this is what it says
Shape shoulders and neck

(RS) Bind off 9 sts at beginning of next 2 rows, then 9 sts at beginning of next 4 rows for shoulders

the stitch is rs row knit, the next row is purl with pattern. so do I bind off just on the right side rows or 9 sts, on the right side row and 9 sts on the purl row?

Does that make sense? I’m probably over thinking this but this has me totally bum fuzzled. Thank YOU

You bind off at the beginning of each row, knit or purl. You can’t bind off at the end of a row, so you always do it at the beginning.

In other words, bind off on the knit side, finish the row. Then bind off on the purl side and finish the row.

Thank you so much. I didn’t know you couldn’t bind off at the end of a row. I’ve never tried and wondered why they didn’t keep the binding off on the same row. Anyway thank you sometimes my brain goes on vacation and leaves me sitting staring at my knitting…