'53 Ford winshield gasket help? Pleease? Anyone?

The car is a '53 Ford business coupe w/o the chrome mouldings around the windows. The gasket they gave me is fine on 3 sides except for 1 which has an extra groove, which I ***ume is the bottom. Does anyone out there know what this extra groove is for. I called Mac's and all the guy told me was it's the right part #.
Thanks Chris

 

Maybe for the beltline trim under the W/S? If thats what it is, that trim goes in first, before the W/S is installed...........OLDBEET

 

There was no trim on the old gasket. Maybe I just need to put it in and not worry about it.