clarified language

Author: marciocloudflare

src/content/docs/magic-transit/how-to/advertise-prefixes.mdx

@@ -30,7 +30,7 @@ List all prefixes and the [autonomous systems (ASNs)](https://www.cloudflare.com
 
 ## Cloudflare ASN vs. your own ASN
 
-When customers supply their own ASN, Cloudflare prepends the main Cloudflare ASN (AS13335) to the BGP `AS_PATH`. For example, if the customer ASN is AS64496, anyone directly peering with Cloudflare sees the path as `13335 64496`.
+As a part of your onboarding process, you need to decide which ASN Cloudflare will use to announce your prefixes. If you supply your own ASN, Cloudflare prepends the main Cloudflare ASN (AS13335) to the BGP `AS_PATH`. For example, if your ASN is `AS64496`, anyone directly peering with Cloudflare sees the path as `13335 64496`.
 
 If you do not have an ASN or do not want to bring your ASN to Cloudflare, you can use the Cloudflare Customer ASN (AS13335).