A song counts for whoever leads it, with all its points. A guest verse doesn't change whose song it is, so a man featured on a woman's hit leaves it hers.
We know an artist's gender from public records where they give it. Where they don't, we estimate it from the artist's name and songs, and count it only when we're confident. Songs by artists we can't place are left out of the shares and shown as not known.
In that month, public records settled 44.3% of the songs we know; our estimates, the rest. We name someone as non-binary in the list only when public records say so, or, for a band, when we're confident it is.