Question about high rent/high income deregulation

So, I got curious about the rental history of the apartment I'm living in and asked for the rent history from the DHCRA. I see that the apartment was rent stabilized through 1998 but then it went vacant and was deregulated due to High Rent/High Income in 2001. From my research, it seems that the rent would have had to have reached $2000 for deregulation to happen but the rent for my place only hit $1500, according to the registration documents filed with DHCRA. Just curious if anyone could comment on how the apartment was deregulated when the rent never reached $2000. Thanks.