Enclosed Balcony 67% calculation help!!!

The DOB law says that balconies count towards floor space “if more than 67 percent of the perimeter of such balcony or terrace is enclosed.”

What exactly does that mean? How do I calculate that?

If my balconies’ perimeter (which I assume means only the 3 sides not counting the side attached to the building??) is 100 inches, does that mean I can have 67 inches of framed glass/plexi going up each of those 3 sides?