Click and hold left mouse key on the left border of the desired range, drag the mouse to the right border of the desired range. When you release the left mouse button, the corresponding area is shown zoomed.
You can reset the zoom by clicking and holding the left mouse button on the graphic, drag the mouse to the left and release the left mouse button.
Click the picture, hold the mouse and drag to the left. If you mouse then
release, the entire measurement is displayed again.