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 30.3% of the songs we know; our estimates, the rest. We name a band as mixed in the list when we're confident it has both women and men in it.