A 15 story building... is the most odd relative measurement to use - wtf?
For a couple of meters it works, I can imagine a 3 meter wide asteroid just fine.
But at 50 meters it becomes a distance unit for me and I can’t easily imagine an object with a 50m dimension. I’ve seen actual 15 story buildings though.
(Subway was sued that the "foot longs" were only 11-11.5 inches in length: https://www.startribune.com/subway-to-ensure-footlongs-measu...)