Thats not too bad... I wish my 22 gallon had that few snails....
My mom has a 10 gallon tank that she has as a temporary home for her dojo's and I swear.... That tank has more snails then gravel. Dead serious the gravel MOVES... At any given moment you can see at least 200 snails.
Those MTS can be a great addition to a tank.. or a tremendous burden.
I just feed mine to my loaches though.. I cant grow them fast enough!