Well, let's think what we'd do for a large-city sized station rotating around a sun without a planet as far as UPP goes.
Port: A - if you built an amazing self sufficient solar-circling city, you must have a big port.
Population: Let's say 7. Let's make it the NYC of the spaceways. 30 million.
Hydrographics: Let's say 0. That covers up to 5% water and you aren't going to get any more green+blue space than that.
Atmosphere: 6. Standard no taint.
Government and Law can be rolled so could be anything.
Tech: I think a minimum for something that big of TL10+. I'd think High Stellar or the high end of Average Stellar, so let's call my example tech level D.
New York has about 28K/sq mile in 303 square miles, but that's not covering the need for agriculture, industry, port space, solar collectors, etc. But all that is inside a station that might be cubical or spherical or whatever.... but it should not be more than 400 km diameter in any event. So we use the 'S' for size.
So we have:
AS607**-D