Censys expands queries to provide additional functionality. For example, the query a:zmap.io
executes a DNS lookup and expands to ip:220.127.116.11.
Your query was changed from:
paypal AND parsed.issuer_dn: "C=US, O=Let's Encrypt, CN=Let's Encrypt Authority X3"
If this isn't what you intended, you can run your raw query without expansion.