You shouldn't talk about intelligence level, because that's not your strong point. You know absolutely nothing about level accuracy absolutely nothing. The first thing concerning the precision of a level is the precision of its bubble, its level vial, the unit of measurement of the level vial is in arc second, 1 arc second = 0,000277778 of degree compared to the horizon, 1 arc second over 8 inches is less than over 9 feet for sure, but the 9 foot length does not by itself make the level less accurate, the 9 foot length allows to a shorter level or a level vial of any accuracy to be able to read 9 feet away, the second arcs remain the same. Your Starrett levels are graduated at 80 to 90 arc seconds, 1 graduation represents .005 miil of an inch in 12 inch, a person can read between 2 graduation lines but.... the level vials on my levels are precise to 2 arc seconds, 40 times more precise than a Starrett, you see I can educate you on precision levels and it's free, I'll include 2 links, 1 for your level and one for my level vial.
The Starrett 98 Machinists Level with Ground and Graduated Vial includes a cross test vial. 200mm (8") size, without case.
www.starrett.com
www.leveldevelopments.com