Add note about per-record CNAME flattening to cf-as-primary/setup

Author: RebeccaTamachiro

src/content/docs/dns/zone-setups/zone-transfers/cloudflare-as-primary/setup.mdx

@@ -25,6 +25,12 @@ Depending on the [settings](/dns/cname-flattening/set-up-cname-flattening/) you
 - For DNS-only CNAME records on the zone apex, Cloudflare will always transfer out the flattened IP addresses.
 - For DNS-only CNAME records on subdomains, Cloudflare will only transfer out flattened IP addresses if the setting [**Flatten all CNAMEs**](/dns/cname-flattening/set-up-cname-flattening/#for-all-cname-records) is enabled.
 
+:::note[Per-record CNAME flattening]
+
+For records using [per-record CNAME flattening](/dns/cname-flattening/set-up-cname-flattening/#per-record) (meaning **Flatten all CNAMEs** is disabled), Cloudflare will transfer out the CNAME, not the flattened IP address.
+
+:::
+
 ### Proxied records
 
 For each [proxied DNS record](/dns/proxy-status/) in your zone, Cloudflare will transfer out two `A` and two `AAAA` records.