Paste the contents of your stats file into the textbox to automatically search for the selected stat. You can find the file here .minecraft/saves/WORLDNAME/stats/UUID.json.
In general, higher is better except for some stats like killed by or number of deaths.
Some entity and item stat combinations like killed by sheep or crafted oak sapling don't make sense. I don't want to go through everything manually and figure out which ones make sense. Just re-roll.