I've got the answer to this conundrum (if I remember correctly, which I am certain I do).
GamePro used to put out a second magazine every now and then, quarterly or twice a year I think, for a few years or so. Some of you may remember it; it was called S.W.A.T.Pro. It was basically a collection of all the stuff from the SWATPro sections of previous magazines, plus guides and the odd review (they reviewd Sonic The Hedgehog for the Master System in one issue).
Anyhow, when they stopped publishing that magazine, they added the issue count to the total of GamePro magazine. That's why it suddenly jumps 11 issues, which means there were 11 issues of SWATPro published over the years presumably.
I remember EGM criticizing them on their issue count and how they did it in one magazine.