Skimmer question -Super Reef Octopus 1000 Internal Skimmer

[Fish Dad]

Has anyone used the Super Reef Octopus 1000 Internal Skimmer, Model: SRO-1000INT looking for feedback and amount of space needed in sump. (description says Footprint: 10.6" x 7.5" is that skimmer or total space?)
I’m just getting into the salt water hobby and trying to design my sump and set up.
The tank is a 55 gallon and I’m looking at a 20 -30 gallon tank for the sump, thinking this is my skimmer. Thanks