IPv6 with DoT

I followed this guide to implement DoT with the Bootsrap IP: https://docs.controld.com/docs/asus-router-setup
It specifically tells you to leave the legacy IPv4 DNS blank.

However, this guide doesn't say anything about IPv6. I'm using the IPv6 Boostrap IP in the DoT configuration, but If I leave the legacy IPv6 blank, IPv6 will not work. How should the legacy IPv6 section be filled?

Edit: never mind, I've restarted the router, flushed windows dns and restarted the PC, it's now working. So it should be correct.
That article needs updating though, ASUS routers already support DoT (no need for Merlin) and it should include IPv6 instructions.