Lead Ratio determines the angle of the ramp in Z during the lead in and lead out. You can specify the Lead Ratio as a number that reflects the percentage of the angle from its default. That means that if you want a lead that is twice the normal ramp length (shallower angle) enter 2. If you want a lead that is steeper than the default, enter .5.
The Lead Ratio value effects both the lead in and the lead out. There is no way to have a separate angle for the lead-in and lead-out. If two numbers are input, only one is used.