You had been working with a 5 st seed st border on each end, but when you bind off the 108 stitches you will be doing that at the beginning of a right side row, that gets rid of the 5 stitch border on that one end. You continue putting the seed st border at the far end, but want to decrease just 1 st at the beginning of the right side rows 2 times. That will put the decreases at the same end where you did the BO and there will not be any seed stitch on that end anymore to be concerned about. Does that make sense? This will be right at the bottom of that long lazy "U" you have on the schematic, to round it off a bit.
Your link didn't work for me, but here is another try for a link to your pattern. LINK