The Bundle tab is only for a single polygon guide for fibers, any other object will ghost the settings on this tab. The polygon guide should consist of a chain of two-point polygons with at least four points along the chain. The quantity of fibers in the bundle is decided on the Geometry tab and then options are applied here.
Bundle - This presents a dropdown with three options as follows:
Count - Determines how many bundles of fibers are going to be created.
Strength - Sets how tightly the Twist or Braid will be applied to the fibers. Higher values lead to an increase in turns involved for the full length of the fibers, which will always extend the full length of the guide.
Spread - The radius of the circle the braided or twisted fibers make. A gradient can be used to reduce the size of the circle as the fibers grow.
Twist - While Strength dictates how the bundles as a group are twisted, Twist twists each individual bundle in the count.