To me a 10 in the real world is one that has a quality repaint in the last 12 months or so, and hangared. A 9 maybe for 12-24 month old quality paint jobs. When people advertise paint and interior as a 9 or 10 and the date of replacement is 7 years ago, I am a little skeptical.
To me a 7-8 is a paint that you are still proud of, had a few nicks and touch ups, but won't need painting for 5+ years.
6's can be old paint that still looks good, just starting to fade a bit in spots.
5's are usually 20 foot paint jobs, any closer and you can see they need painting.
1-4 needs paint, some worse than others.
If a seller ever describes the paint or interior as less than a 6 it probably has an animal living inside and four shades of primer on the outside.
Interior, freshly done by good shop should be a 10, 2 years later it's probably a 9. 7-8 is good servicable interior that you are proud to show your friends. 5-6 needs some dressing up, maybe cracks in the leather, or tears in the pilot seat, carpet could use replacing.
1-4.5 needs interior.