I would take it to mean this:
bind off 11 sts - 8 sts. That means after you bind off 11 stitches, you have 8 remaining.
Work 2 rows even - after binding off the 11 stitches, work the 8 remaining stitches, then turn and work them back.
You have now completed 2 rows. Now bind off the stitches that remain.
If I am wrong I'm sure someone will correct me. It seems like in you're interpretation you turned once too much. the 8 sts after the first instruction is not saying to knit them - just indicating to you how many should be left.
hope it helps,