That's just the simple sequential sense of "first," the first that comes before second, third and fourth; but there's something more radical here than the ordinal or sequential sense of "first."

这只是“先“表示顺序的简单含义,先于第二，第三，第四的那个“先“，但这里,“先“除了表示顺序的意思外还有更激进的含义“

耶鲁公开课 - 弥尔顿课程节选

to get a first down as it's called or second and third and fourth down.

去拿下所谓的第一个10码进攻，然后是第二个，第三个，第四个。

美式足球 - SpeakingMax英语口语达人