Piano pedal marks are somewhat different than other similar Mup statements. Rather than having begintime, text, and duration, each item is just a time offset value, plus an optional "*". If no pedal mark is currently in progress, the first time offset value indicates where the pedal is depressed. Any subsequent pedal items on that staff will then indicate a "blip"--lifting and then immediately depressing the pedal, (which is indicated on the printed music by a "^"), unless there is a "*", in which case it means to lift the pedal and leave it up.
Some examples may help:
1: c;d;e;2.g; 2: 1.ceg; // depress pedal on beat 1, release on 3 pedal 2: 1; 3*; bar 1: g;d;e;f;g;; 2: 1.gdb-; // depress pedal on 2, release and depress // on 4, release on 6 pedal below 2: 2; 4; 6*; bar
See also the "pedstyle" parameter.