How to make a selection of cards from a deck using the SuperMemo 2 algorithm?

Question

Algorithms

There is such a thing as a spaced repetition method for easily learning something (for example, a foreign language). You need to write your own version of Anki . So, I read the algorithm , figured out the formulas. But I can’t understand in any way, according to what principle (according to what characteristic / characteristics (quality, inter-repetition interval, EF)) should I select cards from the deck for fluid training?

Answer 1

> Continue the repetitions until all of these items score at least four.
Add new cards every day. And repeat until the quality of the answer is at least 4.