Summary
When non-standard ports are available, BDS will use the standard ports as the "additional" automatic ports (BDS-1094) rather than ones from the normal random range.

Steps to Reproduce:

1. Modify server-port and server-portv6 to 19131 and 19134 respectively
2. Start server
3. Note that the additional open ports are 19132 and 19133 rather than from the usual random range

What I expected to happen:
The additional ports should be from a higher, unused range

How this impacts server owners:
If you have 2 servers, one that is configured to run on 19132 and 19133 (BDS A) and another to run on 19134 and 19135 (BDS B). If when starting the server, BDS B starts before BDS A it will consume 19132 and 33 as its random ports preventing BDS A from starting (due to ports being in use)

Original description moved to comments for clarity