I'm looking into getting a Jet City 20 watt amp head but I need to know if it can run my 8 ohm cab. It has 8 and 16 outputs but in the description on the website it says it needs to be running 2 8 ohm cabinets in both 8 ohm outputs at the same time. Is this what it means or am I reading this wrong. Can it run one 8 ohm cabinet?

You should be able to use one 8 ohm cab, from one of the 8 ohm outputs. The description on the site doesnt say you need to use both, its saying it has 1 16ohm and 2 8ohm outputs.
gah that's confusing ain't it.
16 ohm for sure.
maybe someone that has the manual can chime in if the 2 8s are wired in series or parallel.

on most amps with labelings like that it means you plug 2 16 ohm cabs into the 8 ohm tabs for 8 ohms series. but that doesn't seem to be the case here.
Prs se Holcomb is the answer
i think i read somewhere that you can use a single 8 ohm cabinet.

dunno what that means tbh. i imagine the inputs are in parallel because there is no indication which input to use if you were only running one cab, which could lead to horrible consequences. it would make sense for them to be in series if the amp is not switchable from 16 ohms. either that or the OT is robust enough to handle mismatches.