Play a little guessing game with her

"I want to make a small bet with you." You reply.

"What do you mean?" She sounds a little intruiged. It must be a very slow day.

"If I can guess two questions - one about the bar, one about you - correctly, I get a free drink. If Im wrong about either, I pay triple price and you can pocket the difference. I got the questions lined up, you just need to confirm my answers."

She pouts her lips a little and mulls it over.

"Deal. Go ahead"

"I will guess exactly how many unopened bottles are left under the bar counter: 36." You obviously already went to check using your superspeed.

The wench smirks a little. There is no way to look under the counter from the seating section, or through any of the windows. She goes back to the counter to count, and comes back a moment later: "you were spot on! So what's the second guess?"