Tube size question

[ieure]

My understanding is that the WTDS indicates the visible size in centimeters. However, the Wells-Gardner D9205 monitor is described as being "33 inches," but has an A80AEJ15X08 tube in it, which is 31.49". 6That's quite a bit less than I'd expect would get rounded up to 33".

Is there something I'm missing here? Perhaps the size is measured laying directly across the screen, which would add an inch or so due to the curve of the face.