Didn't fly it - just hovered

Was a calculation mistake by the student I trusted with it.
The required powersetting was a little on the high side, so just for kicks I re-did the calcs, well - it was already done....
Would you guess what the mistake was?

3top
PS: I was lucky that there weren't just any more jerry cans or it would have been 20 gal over....
Never trust other peoples calcs....