My first question would be: Are you trying to check the rigging on the flaps, or just wondering what each handle setting measures in flap angle? The only rigging measurements are at full up and full down flap positions. Full down is straightforward; number of turns of manual extension crank handle until system bottoms out. Full up has two elements to measure; number of turns of manual handle to bottom out "up", and the gap measurement between the upper flap surface and the wing trailing edge when the flaps are fully retracted using the hydraulic system, after you have properly rigged the flap motor switches to stop at the full up position (and, good luck getting an accurate measurement on most wings' trailing edges...think Ruffles potato chips profile...) The intermediate positions are not actually measured. The actual position/angle of the flaps when being used in flight, compared to the flap handle percentage markings, could best be described as "squishy", and changes slightly depending on whether the flaps were being extended or retracted to a particular setting. Most crews put the flaps at a particular setting they need, and then tweak it to get the desired response from the aircraft anyway.