I know that some numbers are re-used, over the years. For example team
4 is a 2004 rookie. Rookies that year were in the 1200 and 1300 range.
There are a couple of other examples.
The number system does baffle me from time to time. There are almost teams in the 2000 range, and there are only 1130 teams registered. I highly doubt that 45% of teams signed up and dropped out.