Check manual page of printer_output
Generic Printer: Output Unit State
This check monitors the state of output units withing printers. It monitors
the state provided and also outputs the filling state information provided
by the printer.
The printer has to support the generic PRINTER-MIB.
By default the check outputs CRITICAL when either the printer reports 100%
units filled or reports a critical error state. A WARNING state is
raised when a non-critical error is provided.
According the PRINTER-MIB it's possible that a printer couldn't determine
how much is remaining in a supply, so the printer says "at least one remaining".
One check is being created for each unit with a unique name.