2 1/2 quart is not right.
My first question is this a factory trike or converted? If converted it may have been read on the jiffy stand as a two wheeler and that would explain the difference in readings.
We went through this when we converted my Dad's softail into a trike.
What ever capacity it calls for in the manual, especially if it was converted ( go with original bike specs before conversion), go with manual quantity.
The only other thing I can think of if his engine is wet jumping. In that case there is another drain plug in the crank case near the oil drain plug. Pull that and see how much he is getting. It should not be very much at all. If it is alot he has bigger problems.
Hope that helps