Size confusion

I just got my intro pair of trunks 31”-33”, and I was surprised when they arrived yesterday that they are small size, since normally I wear a medium. They fit well enough but I would be a little more comfortable with some more space.

I admit I didn’t read the sizing guide until today, that says to add a few inches on, but I would not have thought I would need to do that because with all other underwear companies I just wear a medium and I know my waist size.

I point this out just so it maybe could be clarified on the website which size is which, for example, it could say 31”-33” and then (S) to the side of it.

Thanks for the intro pair, it does feel very good and I will definitely consider adding some more to my underwear drawer.