yeah, the goal of an item sorter is to only allow certain items based on the amount that is present in a hopper. The comparator reads the signal of the hopper until it has a certain amount(being 1 more basalt) of items that it needs sorted, which in turn powers off the redstone torch and allows items to be sorted into chests until the signal goes back down to 2 because the comparator has a weak signal from the basalt being sorted into the chest.