Definitions of caption
the heading of a legal document, especially one containing a summary of the important information
You'll find the relevant reference numbers in the caption at the top of the document.
the heading at the top of allcourt papers prepared for use during a hearing that gives reference details such as the name of the court, the names of the parties involved, and a description of the document
A cover is not necessary if the caption and signature page of the paper together contain the information required by Rule 32(a)(2).