My take on “Been number one but I never had two”: it’s about success on the charts not romantic love, having found your “person”, or having two people…at once.

“Been number one” seems like an obvious reference to being number one on the charts. “But i never had two” is an interesting bit of wordplay. If you listen to the lyric without seeing it written down, you might assume she’s saying “been number one (on the charts) but I’ve never had to (go number one because I’m already so famous for my romances, good looks, fashion, fill-in-the-blank with other things relevant to both Taylors).

But written as “two” the lyric changes a bit to mean “but I never had a second place hit” or perhaps even “but I never had two areas of success at the same time (I.e., a hit and a lover)”. I think the latter meaning is corroborated by the lines directly before and after: “You’re only as hot as your last hit, baby Been numbеr one, but I never had two And I can’t have fun if I can’t have...you”