We do not put strict limits on Pro Lite volume because different users have different needs.
However, our Pro Lite accounts are an "interactive, single seat license" which means only one user can use the system at a time and the user has to be a real person (it can't be a script, macro or an other automated process). So we do monitor for multiple users and scripted activity.
Other than those restrictions, you can run as many reports as you need.
You can review Pro plans here.