This is a view of a step lap rafter seat on a 8×8 plate. The joint gets its name as the rafter laps over the plate to create an overhang for shedding rain water off the roof away from the side of the building. And as the notch looks like a stair step.
The amount that rafter tail laps over the plate in this drawing is 2″. The step is usually set back the same amount.
I have shown what the step lap rafter seat looks like at the end of the plate as well as two feet on center from the end.
In this drawing the rafter is a 4×6. And it is at a 12/12 roof pitch. The rafter tail will be shown in another detail.