'Must' would seem to imply no fudge factor.
I'm outside that "must" range. I just get a stamp on my medical saying "not JAA compliant", which nobody has ever cared about.
In my case this was because I was flying before the new rules came in and my AME (clearly with the agreement of the CAA) said that the new rules were not intended to ground people who were already flying perfectly happily. He says that the testing shows that I can actually see better (with glasses, obviously) than some of his customers who are within the range.