I’m going to attempt an answer since someone else had this problem.
Some seatposts clamp the rails from the top and bottom. If you know what a Thomson seatpost looks like, those are to to bottom. Some seatposts clamp the rails from the sides. The CG-R is one of those.
Carbon rails are ovalized, with 9 or 10mm being the vertical dimension. Clamps that go top down should be fine with either height. I am assuming the heights are actually different. Given the 1mm difference in nominal dimensions, I would assume this is the case. Note, however, that everyone uses the 31.8mm handlebar clamp standard, but Deda (at one point?) reported their diameter as 31.7mm. I think the actual dimension may have been 31.75mm nominal, but most people rounded up.
I would assume that rails clamping from the side need to explicitly state compatibility with 9mm or 10mm rails. So, if I were in the OP’s position, I would consider using a different seatpost, not that there are a whole lot of direct alternatives to the CG-R. The Canyon VLCS seatpost has a similar aim to the CG-R, but it’s been reported as out of stock for a long time.