When changing the number on the Factory Setup screen, you should enter the actual serial number of your freeze dryer, not just any random number.

To change the serial number on the Factory Setup screen, follow these steps:

1. On the Factory Setup screen, locate the default number '1000' in the middle of the screen.

2. Look for arrows along the bottom of the screen. Click any of these arrows to change the number '1000' to your actual serial number located on the back of your machine.

3. Once you have entered the correct serial number, click 'done' or 'save' in the bottom right corner, depending on your menu.

By entering the correct serial number, you should be able to bypass the Factory Setup screen and proceed with using your freeze dryer.