There's different ones, but I'm hearing 3 hours for that one if you are concerned about how long it lasts. Ask the supplier directly for specs like that.
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.