It will do up to three at a time. I am sure you’ve seen some with up to six or seven stacked up but this is not good practice. This is because for the ultrasonic wave to work properly needs some space. A gap of around 20 to 25mm is needed to make sure the records are cleaned properly. I tend to do them one at a time but I understand people want to do more on some occasions, but they still need to be done properly so three is the maximum that can be done at a time. I hope that helps explain why it is three.