You can sometimes find the exact same battery sold from different places with very different specifications. There is some variation, but sometimes the shop just chooses to stretch the truth far too much.

The 1150mAh battery I currently have in my Palm PDA can sometimes be found advertised as 1500mAh, which is way above what's possible. People have measured this particular battery to vary between just above 1000 mAh to around 1200mAh.