I read "13,750 square foot footprint" as the how much square footage the building will take up on the lot. That would include the outside walls. The building itself will have one floor of retail and five floors of apartments with a total of 113 apartments. According to the rendering, the apartment floors will have less square footage than the retail (ground) floor. Calculating an average of 608 sq ft. per apartment (including hallways, stairs, elevators, and mechanical) is actually generous. The real number is smaller.

I would assume some combination of studios and 1-bedroom apartments. They won't be generously sized. If they're designed well, they could be quite good for a single tenant and tight but doable for a couple.

Rooms at Moxy Hotels are around 180 square feet. If you double that to allow space for a closet, small kitchen, small sitting room, and a stacked washer/dryer, you'd be at 360 square feet.

Of course, all this is just an exercise. The apartments are not part of the Courtyard by Marriott component of the revitalized Beury block.