1/16" difference of the outer dimension? I don't know if that even matters. I have the same cutter and have been cutting mat for my own use. I would consider it within tolerance.

One caution if you are going to trim it to match.....

If the excess is NOT even and you try to trim it, because the excess isn't even and SO SMALL, with different pressure on the blade from both sides, the cutting blade can bend and make the cut line not straight. I've experienced this when I tried to correct small imperfections. Go extremely slow and watch closely as you do this. You could end up making it worse. (I did)