If I understand your question, you would like to set delay time with finer resolution than is possible with the Dly Time knobs.You can use the encoder to do this. Here's how:
As described on Pages 24 and 25 of the User Guide, you can use the encoder to tweak delay times. You must be in Play Mode. Use a Dly Time knob (either A or B) to set the delay time as near to the desired delay time as possible. Next, press the Tap footswtich once. The billboard will display the current delay time. With the delay time displayed (before it times out), turn the encoder to adjust the delay time in 1 msec increments.