no carddav flag

[chattex]

so i got a synology NAS. I got my calender connected to my phone via carddav. works perfectly fine and there even is a flag with carddav.
reaching it via https://name.synology.me:5001/carddav/USERNAME

BUT, if i do as described to connect to my contacts, there is no flag carddav but the exact same flag to my caldav.

https://name.synology.me:8443/adressbooks/users/USERNAME/adressbook
so i want to reach out to my contacts but am only finding my calender via the wrong port, what is happening here and how can i fix that?

mfg, chattex