Yeah! In the "Tips and notes" section it says:
The difference is kēlā refers to "that" which is away from the listener and kēnā refers to "that" which is near the listener. Cultural note of interest: Hawaiians are keenly aware of space and time.
For me, I was thinking of it as -nā for near and -lā for far, like là ["there" as in "over there" in French] to help remember which was which... :D