Potty training help

So we just started potty training today. I got her underwear because she didn't care if she had a wet diaper so figured she needed something where she could feel the moisture better. She definitely does not like wet underwear. She has gone in the potty once so far, but it wasn't a full pee. And 3 times today she has gone pee within 30 seconds of getting off the toilet. I set a timer for 20 minutes and then we will sit on the potty for at least 5 minutes. I need help y'all. She's 18 months old if that matters at all. I've been very patient, of course. Because this is just her first day and accidents happen. But her peeing so soon after getting up can definitely be discouraging haha