When a new software version is detected, is it a major update?

Each time there's a new software version detected I wonder if it's a major update or just a patch or test. It would seem to me that if we had a chart showing the number of vehicles versus days since first detected for the last 5 or 10 updates we could tell by comparing them. If the curve is steeper and didn't plateau it would be a major update. If it was shallow and stopped updating we could probably ignore it.