Out of curiosity, I found a copy of the R10 user manual. It is a Super8 camera. Its metering system's film speed is set by the S8 cartridge. Range ASA 10-400 (daylight) and 16-640 (tungsten).
It has an exposure compensation control that can be varied continuously from 2 stops overexposure to 1 stop underexposure. Normal setting is 0.
In addition, the rotary sector shutter's opening can be set to full (160 degrees), 1/2 (80) and 1/4 (40). Discrete steps, not continuously variable. So in fact 2 and 3 stops of underexposure for, typically, a back-lighted subject are available.
I had an R10. The variable shutter angle was useful for in camera fades and, in conjunction with the in camera rewind, dissolves. For the work I was doing (travelogues), the dissolve facility was useless. I returned the camera because its f/1.4 lens t -stopped around t/3. The Schneider zooms on my Beaulieus t-stopped at their rated f/1.8 and f/1.4.