We define a user as one personalized email address (name@yourcompany.com). Even if this user uses multiple cloud apps (Google Drive, OneDrive, etc.) we still count it as one user.

So for example, if you have OneDrive (cloudhqtester@gmail.com), Google Drive (cloudhqtester@gmail.com) or Dropbox (cloudhqtester@gmail.com) and you sync or backup these cloud apps, that will be counted as 1 user/ license.

1 user is:
OneDrive (cloudhqtester@gmail.com) <-> Google Drive (cloudhqtester@gmail.com)
Google Drive (cloudhqtester@gmail.com) -> Dropbox (cloudhqtester@gmail.com)

In other words, you can think that we are counting users in the same way as Google G Suite or Dropbox is counting users.