Differentiate the time spent when a user was assigned a paid licence

I use the “Time spent” value from the users’ details report (CSV exported from the account settings tab) to evaluate paid licences in use and remove them from people that doesn’t use them enough.

Being able to differenciate between the time for when a user was a reviewer or viewer (non paid seat) versus their time as an owner or contributor (paid seat) would allow me to make more accurate decisions.