It might help to be a bit more specific about what "dark" vs "light" means. Does it only mean how evil vs how good you are? If a character has done terrible things in the past, out of necessity or because it was the best option available to them, but they're still a good person, what does that mean? You could also try giving descriptions so that the numbers mean something, like... "5 = could never hurt anyone EVER; 3 = is a generally good person; 1 = usually errs on the side of good but wouldn't really say they try to be good" or ... something. That way everyone is using the same scale.