AdGuardHome asks for username and password

Just installed DietPi 9.15 on a Odroid C4 and installed AdGuardhome. When I go to the webinterface, x.x.x.x:8083, I have to fill in a username and a password. I have no idea what to fill in here, the default dietpi and root ones don’t work. I uninstalled AdGuardHome and re-installed it again but that didn´t help. What do I have to fill in as username and password here?

Did you already checked our online docs? DNS Servers Options - DietPi.com Docs

For some reason I didn´t found this page when searching for an answer. Thanks.