I am not an expert but I charge my 1300 mah batt at 1.3 amps, 100 at 1 A, and 500 at 0.5 A. That's a 1 C charge rate, considered safe for lipos. The 20C rating is max discharge. The 20C seems kind of light to me, mine are all 30C or 35C.
I forgot what brand my charger is but I pick cell count (7.4, 11.1, etc etc) and can dial in charge rate at tenths of an amp, then press go and wait = about an hour to recharge at the 1 C rate.