The weights on that chart are per tire as noted. But load/pressure also depends on wheel position, as in Single (Front) or Dual (Rear).
Weigh it once, loaded for travel. Divide Rear axle scale weight by 4 and set all four Rear to what the chart calls for Dual. Divide Front scale weight by 2 and set both Fronts to what it calls for for Single.
Note this: It's possible to load the Rear Axle of an E450 to the max load for the specified tires therefore 80PSI.
But! The max capacity for E450 Front axle works out to only 65PSI. Check Ford's label. 65 front, 80 rear. In our case, Jayco simply echoed those numbers on their label. On our first coach, a Holiday, they posted what they thought would work, which was less than Ford's numbers.