Censys expands queries to provide additional functionality. For example, the query a:zmap.io
executes a DNS lookup and expands to ip:184.108.40.206.
Your query was changed from:
parsed.issuer_dn: C=US, ST=New Jersey, L=Jersey City, O=The USERTRUST Network, CN=USERTrust RSA Certification Authority
If this isn't what you intended, you can run your raw query without expansion.