At every company I've worked at any time someone has asked "How many active users do we have?" it was a difficult question to answer because everyone's idea of "active user" was different.

"Active, as in logs in regularly? Wait, what is 'regularly'? Once a week? Once a month? Every day? Does 'active user' mean, online right now?"

Etc, etc...

Their definition of "active user" is relative, not inaccurate.