AMT 165 BR & Yamaha 50. Different RPM/Speed/Economy

Top large number of the upper gauge is RPM (x100. 53 = 5300 rpm) The large number of the lower gauge is speed km/h. And the smaller number under it is consumption - how many kilometers you get by one liter. At top speed 50 km/h & 5300 rpm, you get 2.7 km per litre = 0.67L per nautical mile. Optimum seems to be 4200..4300 rpm & 37 km/h. 3.7 km per litre = 0.5L per nautical mile.