DNS-AS Metadata Resource Record are expressed within a TXT DATA format

+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
/                   TXT-DATA                   /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+


TXT-DATA       One or more <character-string>s.

• TXT RRs are used to hold descriptive text.
  The semantics of the text depends on the domain where it is found.
• Originally for arbitrary human-readable text in a DNS record.
• Since the early 1990s, however, this record more often carries machine-readable data, such as specified by RFC 1464, opportunistic encryption, Sender Policy Framework, DKIM, DMARC, DNS-SD, etc.
• The base DNS specification limits DNS messages over UDP to 512 octets
• You can use multiple RRs, but this will make it complicated to sort the records