This is fairly normal to receive 2 ipv6 addresses, depending on your provider. In my case, I receive a /128 address (single global address), and a /48 address (delegated global prefix). In addition, there is the link local address that will be fe80:.... Delegated prefixes allow your internal devices to be assigned a global address within that subnet and access ipv6 resources directly. Feel free to ask more.

One is probably link local the other is global, that’s pretty normal. https://en.wikipedia.org/wiki/IPv6_address#Address_Scopes

Are both subnets public?

Are both of them ula addresses? (both of them starting with 2). If they are not the same then the ISP is providing an internal unique address for isp internal configurations.

If so, are they having the same network? ( The first 48 bits) if not, then is probably a miss configuration but probably in their side. But with no practical effects. You could ignore it.

If yes again, then it is a miss configuration and it shouldn't happen, but this time it could be in your side, check that the dhcpv6 daemon doesn't try to give an ipv6 address To your Wan port