According to RFC1034 §5.3.3,
In addition to the names and addresses of the servers, the SLIST data
structure can be sorted to use the best servers first, and to insure
that all addresses of all servers are used in a round-robin manner
That is to say, if there are multiple resource records matching the record type of the query, most name servers will return them in a round-robin manner (the additional records may or may not be included in the answer section or displayed by the resolver). My guess would be that you have multiple records for the same domain, each with different content.