Help on Sweater (Shaping Shoulder/Back of Neck)

Hi there, hoping someone can help me understand this part of the pattern I am working on:

Cast off 15 stitches, K until there are 56 st on right needle and turn, leaving remainder of stitches on holder. ( I just knit 56 stitches and turned the work, which stitches am I leaving on the holder? The 56 stitches or all the stitched that are on the left needle?)

Work each side of neck seperately.
Cast off 5 st at beg of next and foll alt row and AT THE SAME TIME cast off 15 st at beg of second row
Work 1 row.
Cast off remember 16
With RS facing , rejoin yarn to stitches from holder, cast off 39 st, K to end.
Complete to match first side, reversing shapings.

( I don’t understand any of this and was wondering if someone can put it in to words that are easier for me to understand :)!)

Thank you so much!!!

Welcome to KH!
You’re going to work with the 56sts. Turn as you would at the end of a row, bind off 5sts (neck edge) and work to the end of the row. Begin the next row by binding off 15sts (armhole edge),work to the end of the row, turn and bind off 5sts.
The bind offs as written don’t add up to 56sts, even if you include the 16 rem sts. Can you give us a pattern link or a pattern name please?

This is a photograph of what I wrote down, maybe I didn’t write it down correctly ! !

Thank you for helping me…I think I understand what you are saying here…hmm

OK, yes, the missing sts are accounted for in the pattern.
You’re going to work with the 56sts. Turn as you would at the end of a row, bind off 5sts (neck edge) and work to the end of the row. Begin the next row by binding off 15sts (armhole edge),work to the end of the row, turn and bind off 5sts. Now work to the end of the row, turn, bind off 15sts. Work one row with no bind offs and finally bind off remaining 16sts.

Thank you so much, so helpful xx