BTS’ latest single “On” shattered expectations, debuting at No. 4 on the Billboard Hot 100 in its first week.

Fans were obviously happy to see the latest single become the highest-charting song for not just BTS, but any Korean group ever.

But what should have been a celebratory occasion soon spawned controversy, as curious fans took notice of an alleged gap between Billboard’s streaming figure for the song -- 18.3 million streams -- and what could be found publicly: around 18.9 million on YouTube and Spotify alone.

The hashtag #BillboardRecalculate trended on Twitter for days, as fans called on the chart company to recount stream figures for the septet’s latest single.

Simon Falk, a music chart analyst who makes predictions for the Billboard Hot 100 on Twitter, says it’s not so unusual to see YouTube numbers not align with Billboard’s reporting.

“The number was certainly on the very low end of the possible range, but still somewhat in it to me,” he said.

Falk put “On” at No. 3 in his final prediction before the chart was released, missing the mark by just one spot.

Brian Cantor, editor-in-chief of Headline Planet, says Billboard normally doesn’t have to defend itself, with its reputation as the undisputed authority for tracking the music industry.

“Billboard’s team and data providers run their own audits and calculations, meaning there is no guarantee their numbers will precisely align with what is available on the YouTube and Spotify websites.”

Nevertheless, he believes this is one of the few times that calls for a breakdown.

“Billboard’s initial article and tweet featured errant data about the music video release. They said the video came out on February 28, which was after the February 21-27 tracking period. As a result, Billboard said the video views would count toward next week’s chart.”

As Cantor said, the Billboard charts incorrectly said the official music video of the song premiered on Feb. 28 in a now deleted tweet last week, before changing the date to the 27th in another.

“The ‘On’ number already seemed low in comparison to the public YouTube and Spotify data, and now fans had reason to suspect Billboard made a mistake in its calculation. Can you blame BTS fans for seeking more clarity?” he continued.

While it could have been a simple editorial typo, as opposed to an error in the chart calculation, Cantor sees where BTS fans come from.

“When the editorial mistake fuels existing speculation about a bigger problem, it makes sense to provide transparency,” he added.

Billboard and Nielsen were contacted for comment but had not responded as of press time.

The error also prompted the company to issues an editor’s note, which said, “An earlier version of this story included the incorrect premiere date for the official ‘On’ video. It has been updated to reflect the correct, Feb. 27 date.”

The note went on to say that the streaming services that currently contribute to Billboard’s charts include, but are not limited to: Amazon (including Amazon Music Unlimited & Amazon Prime), Apple Music, Google, Pandora, SoundCloud, Spotify, Tidal and YouTube.

It’s safe to say what is essentially a reiteration of their chart policy with little detail didn’t go down well, as fans demanded a full breakdown, with some responding with pictures of a calculator.

One fan says it’s not about changing the chart position for “On.”

“It’s been said, but this isn’t about the position on the chart. 4 is fine if 4 is what we got, if we don’t move an inch it’s fine but we want what BTS has earned, we want FAIRNESS. We want everything taken into account. #BillboardRecalculate,” the fan wrote on Twitter.

By Yim Hyun-su (hyunsu@heraldcorp.com)