None of these users is paying at the moment, but that is only temporary. The service was launched at the end of June. The cost for Apple in the UK is £9.99 a month but is free for the first 3 months. They have to let Apple know in advance if they don’t want to stay on as a member.
One of its rivals Spotify has more users, but a big reason for that is that Spotify offers a permanent free option which apple has refused to do. Apple offers a family option which allows up to 6 people to use for £14.99. There have been some reported technical problems which Apple insist are only temporary.
Apple has an advantage because its service is bundled with it on all up to date Apple devices. They’ll strengthen themselves even more when it launches on Android in the autumn.