I'm guessing you're already trying to add it as "Generic Hikvision"?
Have you tried adding under "ONVIF"?
Looking at the Surveillance Station forum, it seems as though there was no support for the Hikvision intercoms recently.
So it might also be worth raising a ticket with Synology support asking if there's a way to add your KV8413 too - unless someone else here has managed it.