Popular in this case should be enough that it is clear that the song should have passed $10,000 dollars in revenue. This should be approximately 4,000,000 Spotify plays or equivalent.

For this market to resolve it doesn't need to be an exact number, correct order of magnitude is fine. e.g.

"Low five figures"

"Close to twenty grand"

If she mentions an amount of revenue shared that is under $10,000, that will not cause this market to resolve "Yes".

It will resolve "No" if a month passes after the song clears the "Popular" threshold and we do not know how much money it earned.