I think it is impossible because it based on Minecraft's tick rate which is 1/20 secs.

600 RPM = 2 Ticks

1200 RPM = 1 Ticks

300 RPM = 3 Ticks

They're literally fixed numbers, and yes, if you adjust from 600 RPM (2 Ticks) to 601 RPM, it will count as 1200 RPM (1 Ticks) somehow.