You might of been kidding, but I wasn’t.Rock crawler speak, it stands for Ramp Travel Index.... Basically how far up you can drive one tire up a steep ramp while keeping the other three tires firmly planted on flat ground. I think it's kinda silly but a lot of guys with serious lifted jeeps get obsessed with it.
(Edit: And to be clear I was totally kidding)
Ramp travel index - Wikipedia
en.wikipedia.org