I think my package said that my extra wide double folded bias tape was a finished 1/2″ but, regardless, if yours is a finished 5/8″ it will still work just fine. It just means that you’ll have a slightly wider bias border going around your apron. While the bias tape is folded up, and just looking at it, if you notice one side is slightly shorter than the other, put the shorter side on the front of the apron so that longer side goes on the back. This will ensure that when you edge stitch the bias tape, it’ll catch on the back. Now when you start opening the bias tape, are you saying the inside folded edges are a smaller width? If that is the case, then do a basting stitch around the whole apron at 5/8″ away from the raw edge. When you open the bias tape, place the first crease on the 5/8″ basting stitch. The raw edge of the bias tape will not meet the raw edge of the apron but when you refold the bias tape, after stitching the crease in place, it should fit the edge perfectly. (this is only if the finished width of the bias tape is 5/8″. If, for example, it was a finished 1/2″ then I would do my basting stitch at a 1/2″ instead.) I hope this helps! 🙂