It's possible to drag the plot either from the edge of the gray area or from the edge of the plot. If you drag the grey area to the right, the 25 meter distance mark also moves to the right. Or if you want to compress the scale with height: drag the plot down from the upper edge. As the other axis remains the same, the scale should be 1:1 in a certain moment. I'd even use a ruler to make sure :-)
If one wants to get more space above or beside the plot: right-click on y- or x-axis (may be quite tricky to get it right), Format Axis, tab Scale, set Maximum as desired and repeat dragging.