It is an interesting question. The problem is the commodity model which these tablets are built. If they run out of one battery, they insert a compatible, but potentially lower maH unit. The worse question is whether the 4000 is really a 4000. I have popped a few tablets back in September. They said in the specs. 1800 and were on the battery only 1600. Thus, unfortunately, you cannot always believe the advertised specs either.
So, I would suggest being a skeptic on any battery listed unless the unit is a higher end tablet.