There are two options to find out how many paper is still in your printer.

When the Print Station is turned on and the app is logged in, you can see the amount of paper that's left in the connected printers. When the app is logged in you are automatically in the 'Dashboard' page of the app. Underneath the Daily statistics you see the printers connected to the Print Station. Underneath 'Prints available' you see the number of sheets that are left in the printer.

The second option is in the Live Preview app. When logging in to 'Live Preview app' with your PIN you can also see the amount of paper left in your printer.