The 16,000 RPM is the maximum RPM O.S. ran the engine out with some propeller. That is about as high an RPM as you can run the engine before it self-destructs. If you have the engine turning that high, then you will not get the low-end RPM stated in the range. The lower end is the lowest RPM the engine could be made to run with some propeller attached. You will most certainly NOT get both ends of the RPM range at the same time. Also, if you use a propeller suited to most airplanes intended to be flown with that size engine, then you will get an RPM level between 10,000 and 12,000 RPM.

We'd consider a propeller that made the engine turn below 10,000 RPM a bit too large. We'll prop the engine to turn around 12,000 RPM...11 x7 or 12 x 6, or other propeller pitch/diameter combination that gives around 12K.