Depending upon the type you are looking at the graphs may be gross (unfactored) or net (factored).
The gross performance data must be representative - no heroics required. In order to achieve very close to those numbers you must fly the aircraft as close to the criterea stated on each graph. Net performance should be attainable by the worst pilot on the worst day in the worst aircraft but there is a limit.
If the approach speed at gross mass is 67kt and you choose to use 75kt (like most clubs that operate the Warrior, for example) then all the net factorisation in the world will be fairly worthless as you burn up excess 1/2rho V squareds (sic) in the rather prolonged flare.
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