Help Pursenalities Plus All In One

Hi

I am in making the All In One bag on page 34 of the Pursenalites Plus book. Can someone explain the buttonhole handles --I have gotten to the point where the buttonhole starts and the instructions says knit 10–Then it has you cast off 25–When you go back to the beginning of the book and look at page 8 where she is giving her buttonhole instructions she says to start the CO to Slip two and bind 1 off and then slip the next stitch and bind off --There are 25 bind offs so I can figure that part out except she says to slide the last stitch to the left hand needle.
Can anyone explain this --I know once i do this once it will be fine–
I tried googling buttonhole handles but the one I read had you placing markers and the Pursenalities directions doesn’t say anything about that.

Ugh

Janice

Whenever you bind off, you have one stitch left. It sounds like you just transfer that to the left needle.