The difference from "your normal" is what's important more than how you count.

I use an incident meter. I measure once with dome pointed at the light source as my baseline. In a cross-lit situation I then point the dome at the camera and take a reading.

The difference between those two readings in late afternoon is normally about 1-stop. I consider that a normal SBR.

If the subject is backlit, the difference between baseline and dome at the camera readings might be 3-stops. High contrast, large/wide/high SBR.

If the subject is front lit the difference is 0, so one stop less than my normal which indicates a small/narrow/low SBR.