When setting up a SIP or IAX trunk and putting multiple permit or deny rules in the "other options" box, PBX Manager removes all but the last one entered when saving it to the config file. The syntax of the file allows multiple of these, and it's necessary when talking to a multi-homed SIP provider who could deliver a call to you from any of a few IPs.
If I put the following in the box:
Then I get the following written to the file:
Using PBX Manager 188.8.131.52