How Big Is a Room With Three Mirrors?

About this piece

One room, one ball, a floor of tiles to crack.

Then a wall turned into a mirror and the room had a twin. Two mirrors made a corridor with no end, until they leaned in and it curled into a ring. A third mirror covered the whole floor of the world. After that only the angles moved. A little tighter, and the endless rooms folded into a circle whose edge you can run at forever. A little wider, and they closed into a ball of exactly 120 rooms.

The first room is the only real one. Everything else is a reflection. So how big is it, really? Tell me what you think.