I'm moving and have been looking into houses a lot recently. I found an app that general shows both sizes, so it's helpful.
The smaller, individual unit size is called 전용면적 (jeon yong myeon jeok). The larger area, which usually includes the hallway/common areas, is called 계약면적 (gye yak myeon jeok).
Just in case they don't state which it is and you want to ask :)