text on Master 20 i can't delete

This means that DMX Input (from ETCNet2 or sACN) is enabled on the console.
When this is turned on, Master 20 is dedicated to 'mastering' this DMX input.

Exit to System Settings, look in the "Output" tab.

The DMX Input section contains an option "DMX Input mode". Turn that Off.

- See "Exit to System Settings" > "System Settings - Output (6.0)" in the manual and online Help.

Thank you