Been awhile...refresher on timing please and thank you

[Pinchecharlie]

So I have a stock gen1 sbc with an aftermarket hei
It's new to me with no real details , anyway
I hooked up my light
And at idle turned the knob until the balancer and tab zeroed out and got a reading of 34°?
This is just with everything hooked up in running condition.
I thought it would be a really low number between 10-18.
Just wonder what iam doing because I've realized lately iam a ****y mechanic lol.
I should plug advance and put in 30-34 ° before 3k and whatch out for detonation ?
Must be doing something stupid because it wouldn't run like that and it runs pretty good?
If you would please enlighten me I would appreciate it. Thanks Charlie