Thanks for the comments guys! I chose to 'let it go' but obviously I didn't completely let it go
Another time I went to practice and I got the balls and they were waxy so I went back up to the counter and asked for a different set because those hadn't been polished. I was told they were all that way and they were freshly cleaned. So I went back to the table, rolled them around and decided I didn't want to practice with sticky balls so I took them back up. Yep! I was charged a half hour minimum.

I refused to pay it and was advised there would be a call to the local constabulary. So, here's $3. Have a nice day.
But yet I continue to go there.
I just like the place. And I'm not giving up my pool hall for a few measley bucks.
But...I don't buy food there much anymore. I don't drink much there anymore. I don't 'hang out' there anymore. Now I'm just there when I have a match of some kind.
I guess I go there, but don't care as much about supporting the business as I used to. My tabs have gone from regularly $50-60 (dinner, some beers, some beers for the other team, some beers for our team, etc...) to less than $10 (one or two beers and tip). The bartender who charged me the half hour minimum has never gotten a tip from me. I don't stiff her, but I make sure I never order anything from her. If she's the only one working I just don't order anything.
I wonder if they know how much that $12 has cost them? At this point thousands at least.
~rc