[clockcycle]

Your phone does not trickle charge itself, that means that when it is full it stops charging and uses the battery.

So even though you just took it off the charger it doesn't mean it just started using the battery and dropped 5%. It just refreshed the display showing what it used since full charge. The 2% additional in 5mins, means it was already gonna drop another 1% and by you watching and turning on the screen, you used up another 1%..

Also another theory would be the same thing that happens when you are watching your clock, time slows down... As you watch your battery usage, the more gets used..

-CC