Right, this is a little bit vague so bear with me:
The transport bar (where all your play/stop/record buttons are, at the bottom) has a litle number where it says tempo, that's your global tempo essentially, everything - the click track, MIDI tempo, will be according to this.
When you're in that drum map, you'll be plotting points out on a grid with the drumstick tool. You've probably figured out that the grid has a set note legnth - if the vertical lines were smaller, you could cram more notes in.
If you want to change the note length of the grid, click the big Q button
and change the little drop down bar next to it to the note length you want. (this means you can end up with 64th notes at 300 bpm..... \m/ )
this image might help.