The group admin's view of a prospective member's form should only show the fields the member filled out. However, due to a bug, all custom fields that that the group has created are listed on the form. Further the fields aren't listed in order. 

Please note that this is only the case on the admin's view of the completed membership form, found at manage > invite members > track invites > approve members. The member will only see the fields that the admin has chosen to include on the membership form. Still, we are working to fix this bug and apologize for any confusion it may have caused you.