ACC parameter is independent from the control mode. It is always a parameter which depends on torque according to time.
If CLP = ON, the torque is linear. If CLP = OFF, the voltage is linear.
Take care because ATS48 is a softstarter and not a drive so the parameter ACC have not the same function.
For instance, if you choose ACC = 30 seconds, it doesn't means that you will start your motor during 30 seconds. In fact, the start duration depends on the load, on the current limitation, on the control mode,
In CLP = ON (torque control mode) if you increase the current limitation ILT, the acceleration time ACC decrease and vice versa. These 2 parameters are linked.