Since it isn't a known race track, you may need to
manually set the start/finish line. It definitely helps that it is the same point since RaceRender seems to handle circuits much better than point-to-point (though it does have single lap support for point-to-point). You might find a little more information
here under the "How to Fix Missing Lap Numbers & Times" section.
If you get exact lap times (perhaps in a printout after the race), you can enter them in the Lap List dialog under the "Laps" button next to the "Create Video" button (don't see documentation on this at the moment). If you're technically inclined, then you could even add them to a raw CSV input file using the
RaceRender Data File Format as noted under the Advanced Features > Precise Lap Times & Separate Lap Info header which is the same format as the Lap List.