If you use battery monitor widget, it graphs your battery level, if you look at my attached picture, if you reboot, it drops, then stays at that level for a while, before continuing on its normal drop rate, this shows that it is reading incorrectly, but in the end, after it gets past that holding point, it is back on track. Look at the overall curve of the battery drain, it stays linear to what it should have been without the reboot in there.
Voltage is a better graph. It doesn't lie like percentage left.