caption

NameTypeDescription
captionStringThe caption (display name) for the custom conversion column

This is constructed from:
Conversion Rule Name + Metric Type ("Conversions", "CVR", "CPA", "Value").

E.g.
"single ring page: Conversions"
"single ring page: CVR"
"single ring page: CPA"
"single ring page: Value"

In practice, each metric type is broken down into 3 entries, like this:

"single ring page: Conversions"
"caption": "single ring page: Conversions (Clicks)"
"caption": "single ring page: Conversions (Views)"
Etc...