回 (kai) means “times” | MotiTan Japanese Dictionary

More examples

この歌を三回聞きます。ko no uta o san kai ki ki ma su

I listen to this song three times.

薬を一日二回飲みます。kusuri o ichi nichi ni kai no mi ma su

I take medicine twice a day.

It treats an action or event as a countable turn, extending naturally from one occurrence to several.

度do: A counter used to count occurrences of an action or event.

動作や出来事が何度起こったかを表す数え方。dō sa ya de ki goto ga nan do o ko tta ka o arawa su kazo e kata

回 (kai, "turn" or "return") is a kanji borrowed from Chinese, and the idea of a turn or cycle extends naturally to counting occurrences.

In common counting expressions, 回 (kai) changes sound after some numbers, as in 一回 (ikkai), 六回 (rokkai), and 八回 (hakkai).