Double Stuf Oreos aren't double stuffed. A high school math teacher in Queensbury, New York had his class weigh 10 of each kind, then weigh the plain wafers separately and subtract them out. Double Stuf came in at 1.86 times the filling of a regular Oreo. Mega Stuf came in at 2.68.
Nabisco said the recipe calls for double the creme and they weren't familiar with what happened in the classroom. Insider ran the same test later and got about the same number.