Both of these members have the same renewal date, 20 July 2009. The field renewal date last changed is only updated if it actually changed (e.g. if the member came from another level which has the exact same renewal date as the group admin then this field is not updated). For an accurate list of new group members use advanced search set to:
match all, membership level is...,member since.. (for new members not previously in the database)
or match all, membership level is..,level last changed (for members switching from other levels)
Jim Sympathy, Fluid Apricot