JLCooper MCS3 USB - Manual (Page 13)

The Wheel Speed slider setting affects the wheel for both
directions of rotation. For the purposes of this example, it
doesn't matter whether you select clockwise or
counterclockwise rotation.
Click on the Wheel Speed slider and drag it to the left.
Now the next time you switch to a QuickTime™ related
application, the wheel will make the movie play back more
slowly, allowing finer control.
The wheel will still produce the equivalent of typing arrow
keys, but with a slower key press repeat rate.
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