How to measure battery capacity (mAh)?
Motorola Droid 4 XT894
has 1785mAh battery with 2% tolerance i.e 1735mAh actual battery capacity.
Your seller seems to have fooled you.
Also it doesn't seem like the seller put up the battery description as 3300mAh by mistake as he has put this in Title name itself

You could have taken out the battery from phone and flipped it to see the battery capacity printed on the other side.  

Side 1





Side 2