In the QEMC, you can know how many Usage Cals are available at the moment. But you can't know how many were available the previous days : in the log, you can find when Usage Cals have been used, but not when they are recharged. So I find it hard to determine if we have the right number of Usage Cals, or if we need more...
See in the technical reference document :
The Usage CAL is designed to accommodate “overflow” usage during peak times. Usage CAL allows any user, identified or anonymous/unidentified, to access only one QlikView application, residing on the server or server cluster to which the Usage CAL is assigned. A Usage CAL allows one user to have access to one QlikView application for up to 60 minutes. If a user exceeds the 60 minute time limitation, the user will have consumed two Usage CALs without any warning being given to the user. Usage CALs are continuously recharged every 28 days (at a pace corresponding to 1/28 of the total number of Usage CALs assigned to the QlikView Server per day)."
Have you explored the Governance Dashboard from QlikMarket? It is free and available for download. In addition, there is a field "UsageCalBalance" as well as other relevant fields to help monitor usage.