The following describes how information is contained in a CFR citation:
Title: Is the numeric value to the left of "CFR".
Part: Is the numeric value to the right of "CFR" and preceding the period (".").
Section/Subpart: Is the numeric value to the right of the period (".").
A subpart is a letter of the alphabet (A-Z) that is used to retrieve an entire subpart of the CFR rather than many individual sections. For example: Subpart E.
Revision Year: The four digit year from the "Revised as of" text represents the year being cited. The revision year is not always available when the CFR is cited.
For example (from FDsys Help, About Code of Federal Regulations):
21 CFR 310.502 Revised as of April 1, 1997