Chance text format: xx, where
1 = lowest chance, ff = highest chance. (hex format)
To remove a chance text (to make sure the note is always played), press DEL.
To control the chance of individual voices in the note duplicator, you can automate the System Chance 1, System Chance 2, etc. effects instead. (Note that the value ff is interpreted as 256 when automating the chance of individual voices in the note duplicator so you don't have to worry about the voices not always playing.)