The chart doesn't list the boost pressure used. In the flight manual as much as 70 in of MAP are listed for WEP at 6000ft using high gear on the supercharger. It
may be a case of how much pressure the supercharger can supply at what altitudes?
It may be complicated by the fact that the engine ratings in the table in the box do not appear to include RAM.
I would note that a few other things on this chart do not line up with what the flight manual says either. Like ordnance carried and max bombload.
http://www.ww2aircraft.net/forum/at...tech/43575d1181164775-f8f-bearcat-f8f-1-2.pdf