Did you read section 5.2.4 of the manual ?

It's strange how the trimpot works in v/f but does not seem to work in vector mode.
Also the motor speed is an issue. It appears that spindle motors are rated at the theoretical speed of 24000 rpm but this is not the actual speed, a thing called 'slip' has to be taken into account.
The manufacturers of my spindle say the slip is about 4% of full speed which works out at 23040 rpm (they said they used a figure of 23100) so this is the speed you should enter for parameter PB.04