WOW! that's WAY off. It looks to me that they maybe made the gasket using a laser cutter or some machine like that and had the "scale factor" about 110% I've made my own gaskets in the past, several actually, and don't have any problems.
Trace the outline on a sheet of material and then, using a hole punch, punch out at least two holes to maintain alignment and put in dowel pins to hold it there.
Next, using your finger, press around on the gasket material to make an impression of all of the inside contours and the remaining hole locations.
Use a sharp exact-o knife, cut out the inside contour, then cut out the outside shape.
Punch out the holes and you're done.