Fluency is much more than being accurate and quick. Being fluent means students can choose flexibly from strategies to solve problems, then are able to explain how they solved a problem, and of course they solve problems accurately and efficiently.
You will notice that there is a video inserted onto each page explaining various strategies students may use to solve single digit problems. This is a very important step in becoming fluent in knowing our facts. If students only memorize a fact, they then only learn that one fact. If they understand a strategy, students then can solve an infinite number of facts. After strategies are understood and practiced, students will then know facts from memory, but will always be able to fall back to their strategy if ever the fact is forgotten.
After strategies are understood, students then can practice their facts using the online games, paper games, or practice sheets listed on each page to help to transfer their facts to memory.