Little help tuning up an old CRT TV?

[BrokenYugo]

What do "Sub brightness" and "AGC adjust" do exactly? Set in question is a Gold Star GCT1954MN, chassis NC-4JA, service data unavailable for free best I can tell. Goal is to to give the thing a quick realignment for a friend to get the most out of the tired tube until he finds a nicer CRT TV for CRT TV things. This thing is old enough it's mostly pots to set it up. I have a basic understanding of how to go through with the service mode line and whatnot setting up the bias, drive, and screen controls, know not to mess with the tuned circuits, etc. but I am not sure where those two fall in to the procedure, or if I should even touch them.   

[mclute0]

Sub brightness = coarse brightness control, brightness would be fine control
AGC adjust = Automatic Gain Control for RF signal, normally not touchy. Does not change picture quality only signal.

always use plastic tweeker to be safe, even if the adjuster can be finger turned.

https://crtdatabase.com/faq/crt-color-adjustment

[strawberry]

should be close https://elektrotanya.com/goldstar_gct2505_cn26b46_chassis_nc44a.pdf/download.html
could adjust Screen to get up brightness

[BrokenYugo]

That does indeed look close enough, pretty concise explanations of what you're looking for with the two controls.