I've checked this and I got it set properly to milimeters and metric. The same seeting is on printer control panel (built-in display) and via administrator control panel (over printer's IP address).
I think the printer and it settings are OK. The problem is with the printer driver which uses US paper sizes as default regardless of printer settings. My suggestion is to let user decide during driver installation if he needs US paper sizes.
I searched our online Knowledge-base and found THIS SOLUTION on changing the units of measurement at the device to metric which may help fix your issue.
I've re-installed printer driver a moment ago because for unknown reason it stuck at US Letter paper size and my configuration changes were ignored. Result was that I were unable to use my printer anymore.
Could anyone please tell me why after installation of fresh printer driver in Windows 10 using the Xerox Smart Start all the settings are for US paper sizes? I never saw a US Letter printer paper in my whole life. I simply don't get why people outside of US are forced to deal with US paper size standards, despite using metric system and international size standards specified in ISO 216.
After such "deafult" installation any person outside of US is forced to find all the places where paper size is set to US Letter and change it manually to A4. This isn't a simple task as this setting is hidden in many places. Failure to do so, results in printer throwing an error that it doesn't have needed paper size. It is also quite comman that any driver update clears user settings and user is forced to deal with the same issue again.
The same story needs to be repeated in every program I use, bacause allways US Letter is chosen by default.
Wouldn't it be better if during driver installation user is asked which paper sizes standards are needed? For example if I only chose "IS 216 - EU paper sizes" option then all US paper sizes like US Letter should be removed from printer driver completely. Choice made by user should be remembered and reflected after future system/driver updates. This will simplify printer maintenance and reduce user stress.