Rcairflr is right on. In hopes to further clarify, the "lands" are basically where the full diameter of the bullet will begin to engage the rifling of the barrel. So, .000" is touching the lands, .005" "jump" means the bullet will travel 5/1000s of an inch before engaging the rifling.
It is an inverse measurement to seating depth - more "jump" or distance from the lands equates to a shorter overall cartridge length (bottom of case to tip of bullet).
Altering seating depth can be helpful in wringing out accuracy - to do it well you need to be able to measure the distance to the lands. Hornady, Sinclair, and some others make tools to this end.
Good luck!
