Hi. I got this error when trying to save DNS Resolver

[1732233510] unbound-checkconf[88932:0] fatal error: outgoing-interface: 10.100.0.2 present twice, cannot bind same ports twice

I searched a bit but, I can't figure out what it means. And to be fair, I have no idea how long this error was in the system as it appears to function normally. I don't necessarily want a step by step guide to fix the error (thanks if it exists). I am keen to learn as I go, but I need to 1st understand what this means. So any translators out there?

Any help will be appreciated.