The chamfer on the collets goes towards the diff.
The rubber seal bit goes towards the diff. But IMO these seals now are a bit too thick, they can split outwards past the washer when assembled. There is only 3.6mm of space in there for them when assembled.
Note that there should be a spring washer between bolt and flat washer- if you don't use it they will definitely split.
The other problem with the latest rubbers is they are just natural rubber, and the oil rots them... what were they thinking...
I made 2 new flat ones for mine out of Notathane front tie bar rubbers- I sliced them off with a Stanley knife and sanded them to 4.75mm thick. Outside diameter is correct.