Looks like there is a bug in the search filters?
Low sales - any theme that has at least 1 sale
Medium sales - at least more that 1 sale. I.e. 2 sales.
High sales - at least more than 34 sales
Top sellers - at least 1.4K sales.
I.e.: 0 = No sales < 1 = Low sales < 2 < Medium sales < 34 < Hight sales < 1.4K < Top sellers
These intermediate gradations are strange.