A stock TJ has about 8" of total travel split 50/50. 4" up and 4" down. Up travel (from normal ride height) should be determined by the bump stop. Down travel (from normal ride height) is usually determined by the extended shock. The bump stop is supposed to be the first limit to up travel just before something crashes into something else. On a modified vehicle the bump stop may need to be extended in order to prevent the larger tire from hitting the fenders (not the flexible flares), over-compressed shocks, steering/suspension components hitting each other, etc.... This prevents damage to the vehicle such as blowing up shocks or in extreme cases prevent s breaking the front track bar which will cause your steering to disappear.
To measure your up travel and assuming that your bumps are correctly extended, measure the space between the axle pad and the steel cup. When measuring, ignore the soft rubber jounce bumper, as this is designed to compress into the steel cup.
Here is a guide on how to set your bump stops.
https://wranglertjforum.com/threads/how-to-set-your-bump-stop-on-a-jeep-wrangler-tj.2474/
This is a very important concept to understand when modifying your Jeep. Knowing how to cycle your suspension, check for clearances and correctly extend your bumps will teach you nearly everything you need to know about how your suspension works. Doing so will help you make intelligent decisions about your upgrades and modifications.
