Sorry...but the drawing and the measurements in the installation instructions are correct and accurate as they only represent the tubs mechanical drawing. In other words... the 7 3/4" measurement for the drain opening in the tub only is only indicating the center line of the "tubs" drain opening to the edge of the tub, it is NOT an instruction or measurement for the actual location of your homes floor drain or instructions on how to assemble the overflow and drain assembly. If you stop and think about it, when setting an alcove tub, there is no way for the folks at American Standard (or any tub maker) to know how far out from the wall the original plumber may have placed the drain in the floor when the house was built, or if your tub will be accessible from from underneath, or if the existing drain line is beneath a concrete slab, and even more critical... they have no way of knowing the orientation of the p-trap below the tub based on things like existing plumbing lines etc. Granted, most typical tub drain kits have a horizontal run from the tub drain to the vertical pipe coming down from the overflow like the one you assembled, but... in many cases, when retrofitting a bathroom with a new tub it is not unusual to have to move the floor drain / p-trap location especially if the new tub is longer, shorter, wider or narrower than the one being replaced. As a result, the engineers at American Standard cannot provide the measurement you seek as they have no way of knowing the potential offset and correlation between the drain opening in the tub itself and the drain opening in your floor. They best they can do is indicate how far the tub drain opening is from the wall. The rest of the drain measurements you have to calculate based on the drain opening in your floor in relation to the wall.
