We have received the required information and replied back to the user, but for the benefit of others we would like to share what we found:
When checking the device tester output for the printer in question we saw that the printer was returning a toner level of -3. This means that there is some toner left, but that the exact amount is unknown, as such Lansweeper won't be able to provide accurate toner levels for the Xerox Waste Toner (Dry Ink) Container, as the printer doesn't seem to return an accurate toner level.