i think this is a good space, thanks for asking!
āPractical Magicā uses JF as a filter for Mangroveās Formant (which is actually the receipient of those Turtle-crawled patterns). JF is only receiving software triggers through Just Type and some light FM from Mangroveās Square. JFās Mix out goes to 3 Sis.
That section (#P) does refer to the Tracker patterns, which has a fence on the first line at 0, 0. TTās Tracker is 0-based, so an end point of 4, 4 would take us five columns over (oops!) and five lines down. I think five columns over was intentional, for syncopation, but adjusting it to four shouldnāt affect the general result too much.
Either way, a fence that includes five rows should have Y range from 0 to 4.