The group contribution feature is not available for Candidate Committees.  It can be used by PACs who receive the same amount every month from the same filers.  For example, 18 members of a union who each have a monthly payroll deduction of $10 sent to the PAC as a contribution.  These donors can be combined into a group.  Each month, the group is selected in a single transaction, but each individual contribution appears on the C3.