I should know this as it's possible I supplied it!
Top front (nearest barrel) is magnet screw i think (check if it's magnetic)
Top back is Pre travel stop screw.
Middle is micro switch adjustment.
Bottom is post travel stop screw.
Don't adjust the magnet screw to far or you will negate the pre-travel screw.
Don't have a long pull and long switch adjustment or you might break the switch.
Erm...that's about it.