For the Survival Range, I was thinking along the same lines as Daniela: to me, it's the zone the party can explore without running into monsters that are too hard for the party's current level. I have very fond memories (insert sarcastic tone here) of certain places in Star Ocean 3, where while exploring a perfectly safe area, you could stray just a teensy bit and get owned by monsters that were suddenly twice your level. -_-
The distance that the party can walk without staying at an Inn (or equivalent) doesn't only depend on your level, after all. It also depends on the play style: a item hoarder can stay alive way longer, for example; and someone who has mastered all the subtleties of the battle system, who knows the monsters well and has a good sense of strategy, will also survive for a long time without needing to rest. So that kind of "survival time" is a bit subjective to be defined clearly, in my humble opinion. :)