Where should an elasticated bottom of a top sit?

[UName38]

I don’t have style or knowledge just wear basic T-Shirts. Where should the elastic on a top like this sit - makes a difference to the size I’d need.

Im sure it will have been asked before but MN search doesn’t work at all and google told me how to sew it.
Thanks from clueless dresser

On the waist, so the excess fabric flops down to create the bubble hem.

Well I'd tuck my belly in nice and snug

That teeshirt is in my basket already!
I've assumed the elastic will always work its way to the smallest part of you.

Thanks