When the pot on the stepper driver is adjusted, it changes the voltage Vref. The current is calculated for each Vref, by a formula that is on the driver ic datasheet or in this case also on pololu website.
The potentiometer on the stepper driver pcb is in a voltage divider, e.g. it changes the voltage continiously and normally it cannot "jump". If it "jumps" it may be because its a carbon track pot, and its carbon track may be damaged, which means it needs replacing.
The potentiometer on the stepper driver pcb is in a voltage divider, e.g. it changes the voltage continiously and normally it cannot "jump". If it "jumps" it may be because its a carbon track pot, and its carbon track may be damaged, which means it needs replacing.