A Legend's average is taken from up to 500 scores. Therefore, the minimum change is 1/500 = .002
@Tom: Nice 30 you shot. It's 60 in the average calc, perhaps taking 4/200 (*) off your average of 64.23.
(*) depending on the no. of ranked Legend rounds.
@EATCAT: A 64 may not mean much to an ave. of 64.25 (about 50 scores). The previous 31=62 should have had a wee impact, didn't it?