At first, you may find that tough Verbal problems—especially Critical Reasoning and Reading Comp—seem arbitrary and subjective. But, they’re less subjective than they seem. GMAT Verbal problems all go through an experimental stage, where they aren’t counted towards your score. A problem is only used on the real GMAT if, during that experimental stage, high scorers consistently get it right and low scorers consistently get it wrong.
The Cambridge Dictionary offers several meanings for towards. In this context, it means "for the purpose of (buying or) achieving something". So "not counted towards" means they are not used in the calculation of your final score.