Bind off twice, then once?

Hello, I am working on a sweater pattern and it says:

Working both sides at once with seperate balls of yarn, dec 1 st at each neck edge (every row) 3 times, and at the same time, bind off at each arm edge 7 sts twice, then 7 sts once.

Why is that not “7 sts three times”? Why twice, then once? And am I binding off every row, or only ws or rs rows?

Help Please!!

Thank you!

You should be binding off from the armhole edge for each side. So for one side of the sweater you bind off on the RS and for the other side of the sweater you bind off on the WS.
Is it possible that there are different directions for different sizes and for your size it happen to be 7sts twice then 7sts once but for other sizes the numbers of sts vary? You’re correct that you just bind off 7sts 3 times on each side.

Since you can’t BO at the end of a row to bind off ‘each arm edge 7 sts twice’ you will have to BO at the beg of the RS row, then the WS row, then again on the RS and the WS rows. You might be left with only 7 sts at that point too, so that’s where the 7 sts once comes in - BO the remaining 7 sts.