[Dynam0]

SMO recalced the score to turn 1 boo into a good and 2 greats into perfects, that pushed the DP over 80% and gave you an A. This happens when getting a timing value that's just outside of the normal judgement window (for example +/- 22.6 ms would still be a marvelous even though it's slightly outside the normal marv window of 22.5 ms). SMO does this to remove false positive perfects/greats etc. caused by server lag (?) and the result is this recalculated score that is roughly equal to judge 3.999 or something. Your 'actual' score would have been the 79.5% B you saw at the start. Most people try to screenshot the unadjusted results because they're more accurate.

I personally haven't seen/had an adjustment that big so this is interesting considering mods like brake shouldn't have an affect on the windows, only visually.