My chances with IUI

So my IUI was yesterday and they always say there’s a 20% chance with IUI. I can’t wrap my head around the fact that it’s always 20% even if you have multiple follicles. I did letrozole and trigger and had 3 or 4 really good ones and 2 more that could have caught up. Husbands post wash sperm count was 329 million! Is it possible that my chances are still that low with these numbers?!?!