The connector is centered between the mounting holes. API500 stuff is centered. You can also use this connector to build dbx900 modules by chopping off the "wings" on the ends and punching holes to match that spec. dbx900 stuff is offset from center.
I think I wasnt clear about the offset.The offset you're talking about is heightwise (in the Z direction) but I was curious to know the offset between the mounting centerline and the the card centerline(in Front View).The DBX and the 500 series seem the same.