First try - Page Appearance

Hello folk at MuseScore forum
I have just finished installing MuseScore on my Linux Mint 18.3, which has a 1920x1200 display.
The default page seems to happen twice, as seen in the screenshot.
Anything entered or done in one page, also happens in the other.

The boundary between the page displays can be moved up or down, using the mouse, by click+hold and dragging it.

Is this normal? Is it perhaps a feature I do not yet understand how to use?