You're not an astrophysicist. I met your mom isn't, either.
Seriously, this isn't a matter of common sense, but of a scientific jargon / English mismatch, it happens all the time. In the context of astronomy, it's completely normal to talk about size in terms of mass rather than spatial units. If somebody asked what size a star was, an answer of "5.6 solar masses" would be a perfectly acceptable answer.