Why would a girl give me her number instead of just taking mine?

I am just curious about these kinds of little nuances.

I ask her to take my number down. She says to just take her number and text her so she has my number.

There has been no verbalization of romantic interest because we work together, and I want to play it safe. That being said, she has to have at least an idea that I'm interested in her. I have no idea if she is interested in me though. There was once a time I did think it was possible, but our jobs actually had us apart for over 2 months, and I never had her number, so it would have been weird to just tell her I'm into her right after. I had this cute idea of giving her my number on a napkin but as I was about to do it, she said to just take down her number and text her.

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It is definitely her number by the way. Confirmed
Why would a girl give me her number instead of just taking mine?
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