Your best bet to undo the kfb is to slide the two stitches off the right tip and gently pull out the yarn, leaving the original loop. The just slip that on the left tip.
If you start with 60 stitches and increase by 24 stitches, you're going to end up with 84 rather than 72.
You're increasing 2 stitches for every 4 worked, so 60 divided by 4 would give you 15 sets of 4 stitches, thus increasing 30 stitches (15 x 2).
So I would say you did it correctly and that the math of the directions is wrong. Since it's a ruffle, I say leave it.