Zoom Out reduces, and Zoom In magnifies the scale.
 

To Zoom In, position mouse at point of interest and left-click.  Alternatively, you may use the right-click menu.

To Zoom Out, position mouse at point of interest, hold either Shift-key, then left-click.  Alternatively, you may use the right-click menu.
 

Levels of Zoom:

UTM Coordinate System (native to 1:24000 and 1:100000 series)

cm per pixel	pixels per km
32000	3.125
16000	6.25
8000	12.5
4000	25
2000	50
1000	100
500	200
250	400
125	800

GEO Coordinate System (native to 1:2000000 series)

millionths of a degree per pixel	pixels per degree
32000	31.25
16000	62.5
8000	125
4000	250
2000	500
1000	1000
500	2000
250	4000
125	8000

Copyright © 2002 by Dapper Mapper