They are literal days but also have mystical signification.
E.g. The sea (of our earth) normally signify the world.
Rock normally signify Christ.
The sun sometimes can signify Christ.
Christians can signify stars, candles, salt.
Jerusalem can signify a place.
Babylon can signify a place.
Babylon can signify Antichrist.
All the examples above are different interpretations amongst 4 kinds of interpretation.

1. Literal (make sure they don't contradict. Make sure they are not exclusive).
2. Moral (you can derive many).
3. Mystical (etc.)
4. Anagogical (etc.)

Before an interpretation is declared to be held universally, theologians can argue.
A new modern rabbi can even say that 7 days is 2 days and we will begin to argue.
Now we have AI image generation. If something about God is difficult for you, you can think of modern invention.
Theory of evolution by Darwin and others is surely rabbinically modern.
God chose to create man on the 6th day (days are equally marked), and rest on the seventh.
The sun was marks the day for us.
The moon marks the seasons/months.
The stars mark the year.

All these are what helped us arrive at our Gregorian calendar.
If you want me to read your source, please post a link to the rabbinical scholars, because money is capable of damaging a long standing tradition.