You will have to ask some questions, like is this frost or tint, is it 80% like coming through or is it blocking 80% of light.
Architects like designers are full of bulls**t like this and to be quiet honest 80% of the time they haven't an idea what they have specified, they just think it sounds clever!
I would ask from what supplier the specifications they require are from. I bet you they don't know!!!!
SC