Well, iono how similar TSC chart creation's interface is to TUSC, but judging from talks with mike while KC Special charts went up, I'm guessing they're close enough. I don't remember dealing with an Absent category when making TUSC charts, but iirc weight and categories were self explanatory. There's really no reason to change the weight from 1.0 for anything because it does naught but create controversy, and the categories should just let you select Time Attack, Races, and Extra from a drop-down menu if the interface is the one I know.
My best guess for absent would be to say 0, for no total. Afaik if you're missing a time stat on the normal charts you don't get a total stat and therefore have one-below-last place credit. The example being 60000 does kind of put me off, though...