Sunnyday,
I have some (maybe) good news for you...
According to the manufacturer of the battery you (and I) bought, the 20ah is NOT 20ah, it's 21Ah!
(Supposedly, he uses 3ah Cylindrical cells in an 8p configuration)
His BMS is set (again supposedly) for 2.05v per cell which is too low, however MY controller is set for 2.6v, so I'm safe for sure.
Have you tested out "full" range or AH yet?
(P.S. Make SURE you don't drain past 2.6v per cell or 41.6v for pack and see how many AH you get)
When I get mine (36v), I will test it out that day (and prolly night too!)
(I will run about 10, 10mile "runs" (at full throttle) to "break-in" the pack and then run my pack from full (39.6v or 3.3v/cell) to "empty" (32.4v or 2.7v/cell) and let you know how close the manufacturer's specs are to actual.