Well, God in his infinite wisdom counted the day & night, obviously. One Mississippi, two Mississippi. Ah ah ah! Three Mississippies!

Granted, it’s just a fictional book we’re talking about, but it does start off with:

And God said, “Let there be light,” and there was light. And God saw that the light was good. And God separated the light from the darkness. God called the light Day, and the darkness he called Night. And there was evening and there was morning, the first day. [Genesis 1:3-5 ESV]

So, within the fiction of the book, there was some sort of other light created before the Sun, doesn’t really make sense that there would be words for day/night/morning before the Sun existed, but maybe there was a temporary light and that created day cycles, whatever. Nitpicking the bible about literal interpretations of things in Genesis seems almost pointless though. It’s stuff that’s easy to dance around and can be hand-waved away.

The bible is probably supposed to be interpreted metaphorically in alot of parts, so pointing out semantic things like this is the equivalent of responding to a long political post with

“You’re”

As if pointing out a single grammatical flaw somehow destroys their entire argument. This was probably meant to be fluff, just someone speaking poetically about an event that nobody would ever know anything about anyways.