They don't give away the details of the calculation, so why should they show us results in details? This would only give us a realistic impression of the grind included.
My opinion: Don't worry too much about it, just play. The progress of average ain't important. Eventually, you need 500 scores which make up a 60.000 average. Most players (like me) suffer from high scores, you suffer from a low number, as your average ain't saturated obviously. Play on, it will happen!
You should only know that scores on Par3 and Par5(!) courses do not count in. Also, I second K's advice to play other courses than KIA - this one is difficult for Legends!
Those who want to get better information must make a note of their ranked rounds # when they tier up. In your situation, with some effort, the number of scores in the mix may be calculated.