番refers to a turn, a number, or a watch/guard duty. The kanji originally referred to the order in which farmers took turns guarding their fields. It is now used for numerical order (e.g., 一番) and taking turns.
That is how Fuguro works. It brings 番 back for review right before you forget it, each time a little later, until it sticks for good. You hear it spoken aloud, and you meet it again in stories you can already read. The first five levels are free.