RPM indicate rotational speed, but by themselves they do not describe how much water remains in the clothes. Radius, distribution, duration, fabric, and drainage also play a role.
Speed and extraction
During the spin cycle, the load follows the drum and some of the water can pass through the perforations and reach the drain. The acceleration related to spinning depends on the radius and the square of the angular velocity. That is why two drums with the same RPM do not necessarily have the same extraction condition.
The maximum on the control panel does not guarantee that all programs will reach it or maintain it for the same amount of time. The stability and distribution can cause the control to reduce speed or repeat redistribution.
What residual moisture means
One way to express it is to relate the water retained to the dry reference mass according to the test method. Illustrative example: if a 5 kg dry load weighs 7.5 kg after spinning, it retains 2.5 kg of water, equivalent to 50% of its dry mass. That calculation does not assign a class without knowing the applicable test.
The spin efficiency classes use their own conditions. They do not transfer directly between methods or replace program capacity.
Relationship with the subsequent drying
With less water retained, there is less water left to evaporate if everything else is comparable. The effect on the energy and time of a washer-dryer also depends on the system and the drying target.
The speed must suit the fabric. Spin drying does not use heat to dry and does not guarantee clothes that are ready to store simply by reaching a high number.
Compare residual moisture and test conditions along with the RPM, not the maximum speed as a standalone indicator.