I just spent 1 hour and 23 minutes firing at the final boss with one of the highest damage weapons, when it finally died the mission time said 543 seconds...this makes sense how?
To Cheden4: I'm pretty sure it glitches your location in the map, not the map it'self.
I haven't bothered trying to figure out exactly why/how since I'd pretty much have to make a new game for each test instance but it probably either fails to register movement involving the destroyed area properly or shifts the map to 0/0 and leaves you in the middle of nowhere thinking its perfectly on center.