MMPO,FPP refers to MinMax (Pairwise Opposition) breaking ties in best score by electing the candidate with the most first preferences (on the unmodified original ballots).
Since MMPO returns ties relatively often, a tiebreaker is needed. FPP is the most obvious one, and also doesn't differ much from other tiebreakers. The comma notation in "MMPO,FPP" signifies that one doesn't eliminate the MMPO non-winning candidates before counting first preferences.
49 A 27 B>C 24 C 100
MMPO,FPP breaks the MMPO tie between B and C by electing B, who is not allowed to win according to Plurality.
It can easily be shown that electing C instead would result in a Later-no-harm violation, because if the C voters add preferences for B:
49 A 27 B>C 24 C>B 100
It's not possible for a sensible method to elect C anymore.