Chopping samples with JJOS 28XL with MPC2500 question

While in the the slice sample screen to edit how many slices and editing start and end parts of each slice it seems that the only way to pinpoint the exact start and end points is with the jog wheel which skips to greater amounts of numbers other than one. Is there a way to exactly punch in the exact number where you want each slice to start and end? I've tried the same way to edit the start and end while trimming a sample in trim mode and it doesn't seem to work. I've also noticed that when you select "do it" after editing the slices the chops aren't exactly where they were when I'm finished editing the slices of the sample I'm chopping. I'm hoping that pinpointing to the exact number I want to start and end each slice will eliminate this issue. Has anybody else ran into these issues? Any info would be great. Thanks for reading.