Ralf, I'll assume you are asking about the ashtray the one in the dash and not the optional one in the lower console.
The manual (first picture) shows the 359422-S bumper (item B) on what I would call the face of receptacle assembly (item 1)
The reality (second picture) from my 67 shows a hole in the same plane as the upper mounting screw (item A) 52721-S8
I don't recall removing this before the restoration so would ask if anyone else has a picture of the bumper, installed, that would be appreciated.
I should add that on the dash lip, the hole on the left (with the screw) is large enough to let the screw pass through and grab the receptacle assy. For the hole on the right, there is no receptacle material behind it, so it was clearly not meant for a fastener, so a bumper does make sense for that location.
I'm wondering now if the diagram is different from reality due to it being revised for a modified design, possibly for 1968.