"Robert Allison" wrote in message

No, united inches is some kind of arcane measurement for estimation
purposes. UN = heighth + width (in inches)

So, a 3' x 4' window would be 36 + 48 = 84 united inches

Stupid, huh?

Yes, but they have been doing that for decades that I know of. All windows
were priced that way when I was in the business. Typical windows may be 30
x 42 or 72 UI. That 600 UI deal does not allow for many windows in a house.
I have 17 windows at about 72 or 66 UI each. They are allowing for about 9
windows in the advertised price.