Between two connectors you find the total fixed resistance, which is specified as nominal value on each potentiometer. In the circuit shown you measure with your multimeter the resistance of a trimming potentiometer with a of total resistance R = 10 kΩ.
Your multimeter measures a resistance of R = 10 kΩ. This value remains unchanged even when you turn at the trimming potentiometer with a screwdriver.
But what will be the result when you use the third connector...?