Because you are using the extend mode. In extend mode, the Mast 22 is an extension of your computer. To correctly use Mast 22 in extend mode, follow the steps below:
- Right click your desktop to enter Display settings.
- There are 1 and 2 in the top, click 2 which represents Mast 22. You could click Identify to know what 1 and 2 separately represent.
- Make it the "main display" in the bottom.
- If you want to make Mast 22 show same as your computer, change “Extend these displays” to “Duplicate these displays” in Multiple displays.
- Go to System Preference-Displays-Arrangement.
- Make Mast 22 the main display: move the “White head” from your Mac to Mast 22.
- If you want to make Mast 22 show same as your Mac, click Mirror Displays.