Hi, Lacko!
You can find the answer in the Step Recording section of the Reference Handbook (more specifically, page 83), although it is... not very clearly explained. The numbers in the last two columns represent the length (duration) of a note event... and are only used for note events. Although internally stored as a MIDI file, which does not have the notion of a note's duration, to make editing easier, the interface combines the note-on and note-off messages in a single event with the start point (i.e., time of the note-on MIDI message) and duration (i.e., difference between the time of the note-off MIDI message and the note-on MIDI message).
I hope my explanation was clear. Regards!