So basically:
6 = Competent
7 = Skilled
8 = Professional
9 = Skilled Professional
10 = Local Guru
?
Mmm. Mooore like
1: Barely trained at the trade/profession/art, etc.
2: Basic principles.
3: Just competent at common tasks.
4: Practiced at common, just starting intermediate
5: Skilled at common tasks, practiced at most intermediate
6: Practiced at intermediate tasks, starting advanced
7: Skilled with intermediate tasks, practiced many advanced
8: Practiced at most advanced skills in the trade/profession/etc.
9-10 Really degrees of fine tuning in your preferred subfield.
All of these beyond 2 or so would also have related skills, of course. A plumber or computer hardware "tech" would quite likely have 3 or 4 main skills at similar levels.
"professional" and "expert" and "master" are pretty non-descriptive. A pro makes money from the trade, more or less steadily.
These are aimed at actual dice results and relative pay levels.
I mean, at Electronics 1 you could look up the bypass procedure on Google and try it. I wouldn't stop you. Of course, I also wouldn't tell you the difficulty other than Google says "Advanced!" or something.
15 is Average. That means that a person with a 5 rating and a 5 stat can do 50% of the time, without special gear. Roughly. So, something like hacking into the hardline would be above Average, yes, although probably not crazy above it. Doing it and bypassing countermeasures installed by one of the most powerful entities in the Cyberpunk world, (the hilariously named Internet Corporation, to whom "even Arasaka pays it's bills"...as if they don't pay their bills?!) now THAT is harder.
Of course, you could just ride the Colonial Studios feed in. Or use the Dataterm and have the IP check go somewhere else, which uses non-hardware skills. If it works...it's a common Netrunner trick and, well, you know Hellhounds.