This option lets you bake (or Plot) animation at export time.
When you activate this option all unsupported constraints and controllers, including the 3ds Max Biped, are resampled into animation curves. You can then import these curves into another application that does not support these 3ds Max constraints.
The plug-in takes the Start and End values automatically from the “timeline” current settings of the host application. You can modify them by changing the values once you activate this option.
The Step value defines how many keys are created per frame, and has a value of 1 by default. Setting a Step of 2 for example, only bakes and exports a key every other frame.