So for 1 sec at f4:
Adjusting shutter speed it's 1 x 2.15 x 2.5 = 5.375 sec (adjusted for RF) at f4.
Adjusting aperture it's 1 sec at f4 + 1.1 + 1.3 = roughly f1.8 (2.4 stops).
Or my original exposure becomes effectively 1 sec at roughly f9.
Do I have that correct yet?