oneHitWondersCount counted artists scrobbled exactly once total, which excludes anyone you've replayed the same single track by dozens of times — despite the UI already labelling this "One-hit wonders", the idiomatic meaning (and lastfm-stats-web's definition, which this app's z-score/Eddington code is already ported from) is "known for exactly one song", regardless of play count. Tracks each artist's set of distinct track names during aggregation and counts artists where that set has exactly one member.