Yes, I know, The point is that, right at the end, she realised that it is a phantom number. According to Google, phantom numbers are:
Non-existent concepts that hint at deeper structures, like irrational numbers (which seemed imaginary at first) or abstract objects in advanced maths that lack literal reality but have huge consequences, such as certain algebraic structures or "ghost" maps in topology. It can also refer to puzzles like the "Phantom X algebra" (a trick proving any number is zero) or educational activities like finding a "phantom function" in game theory.
Historical examples are:
Irrational Numbers: Initially seen as strange or non-existent before being formalized.
Imaginary Numbers: Once considered "fictitious," they are now essential, allowing complex numbers to exist.
Negative Numbers & Fractions: Early concepts that expanded the number system.
Which doesn't leave me a whole lot the wiser.