Reset button - resets the light to zero
Tach/Adv - Toggles between the tach setting and the advance settings.
Flash - On/Off for the strobe
Dec - Decrease the setting
Inc - Increases the setting

Basic use. Hook up the battery leads, Clip the pickup on cylinder number
one. It should come up and ask you to select number of cylinders.
Now it will display the rpms of the engine and can be used as a standard
timing light.
To use the advance feature you need the specs for the engine. They will
tell you that base timing should be something like 4 degrees at 500 rpm.
and that full advance should be something like 30 degrees at 1500 rpms.

Now use the Tach/Adv button to select degrees. Use Dec/Inc to adjust
that number. Then switch to tach and adjust it to the correct number.
When you use the light set properly it will read zero degrees at the set
rpm IF the timing is correct. Use the same thing to check full advance.