Sounds pretty normal to me, I was astonished how much oil it takes to fill up the engine oil ways, oil pipes etc when I filled up with oil for the first time after the rebuild, it seemed to take loads of oil and take forever to fill. And then when I had run it for the first time the oil tank level had dropped dramatically. So re check it after running up the bike.
If your bike has been rebuilt the sticker on the tank may be a generic one, I know that the one on my tank is. Just checked in my handbook and it to states 3.5 litre.
Cheers
Den