Apple Logic Pro 9 - Manual (Page 736)

Maximum Note Length
Sets the maximum length of all note events.
Change the Length value field in the Operations area to define the maximum note length.
Existing note lengths—which are shorter than the length defined here—are retained.
Events that are longer than the defined value are shortened.
Minimum Note Length
Sets the minimum note length.
Change the Min value field in the Operations area to define the minimum note length.
Existing note lengths—that are longer than the length defined here—are retained. Note
events that are shorter than the defined value are increased in length.
736 Chapter 26 Editing MIDI Events in the Transform Window