CRAM: Number of Questions Per Item Question

Hi everyone! I’m hoping to get some clarification on the “Number of Questions Per Item” button on Cram reviews. Is the sentence selection completely random, or does it prioritize sentences based on what grammar points you’ve completed, or some other system?

Asking because I’d like to cram LOTS of sentences, but I want to limit the N1-N3 sentences since I haven’t studied that material yet.

Thanks,