Hermione keeps on thinking, keeping her mind occupied, as she trudges through the snow. And when she comes to the fresh tracks, she decides to follow them.

There could be something missing from her equation. It can be challenging for the equation to calculate the many different possibilities that exist in the Nexus.

Perhaps it is a creature who has her clutch, instead of a person, and so Hermione adds the animal rune into her equation. To see how that effects the results.

And perhaps there is other magic involved. After all, after meeting Felix, Horvath and Danny, Hermione is quite aware that there are other magic users. So she adds the magic rune into her equation.