Let - p := subscription price

- N := number of subscribers

- P:= total spotify money = p * N

In first approximation, let us consider that all subscribers listen to the same amount of music per month

- v := number of minutes of music per subscriber per month

- V := total number of music listened to = v * N

Then, by listening to a minute of an artist, the amount you add to that artist revenue is approximately

P / V = p / v

Which is a fraction of a non-infinitesimal number (in that first approximation)

You got confused by a fact that an infinitesimal number times an infinite number can very much be real