It's approximate. It may be that the capacity was slightly worn from being manufacturer tested prior to being shipped just to test that it works. 60 mAh is negligible. If it's something like 150-200 or above, then you'd probably want to get it replaced with a new one. I've never had any issues with iFixIt products not working or them being used. They also do have a guarantee as well, so if it's not as it should be, you can get a replacement at no extra charge.
