I agree that saying 'billions of universes' is not an exact number and can vary within a range of finite numbers, but it definitely does not include 'infinite billions' (I didn’t quite understand the part about infinite billions you mentioned, but from what I understand, that wouldn’t make sense. 'Billions' always refers to a very large number, but still finite, which goes up to 999 billion, 999 million..)
Regarding Tikki, I don’t think it would be practical or necessary for her to say an exact number, like '724 billion, 482 million, 162 thousand and 62 universes,' especially since her statement is clearly simplifying things. But the fact that she simplifies it doesn’t change the fact that she sets a clear limit by using 'billions.' She doesn’t leave any room for the idea that it could be infinite or something beyond what she mentioned. Also, the point about her not realizing the arrival of another Tikki makes sense, which could indicate that she doesn’t have absolute awareness of all the universes in real time, even though she exists in them simultaneously. This reinforces the idea that she doesn’t necessarily know everything about those billions of universes, even though she knows of their existenc