Crystal Reports 2008 Grouping Problem

I am trying to group by the invoice date and the dates in the grouping header is off a couple of days from what is on the detail line. Look at the jpeg pic I have attached.

Allame should be 7/15/2013,  Allcoa should be 6/12/2012

I would appreciate any help.

                              Thanks,

                               Jerry
Problem-with-grouping.jpg