This variation contrasts the on-string martelé stroke and the off-string ricochet stroke, one loud and the other played at a soft dynamic.
It is useful to think about the role of the first finger on the bow here. The index finger is important in martelé stroke (especially at the tip of the bow) but much less so during the ricochet stroke.
In fact too much pressure from the 1st finger during ricochet can crush the bounce making the stroke uneven.
Practice using the first finger for the first 3 notes and then taking it off the bow for the ricochet stroke.
This exercise is good to develop balance in the bow hold and also makes us aware of how much we may use the 1st finger without thinking.
Try using the side of the hair for the ricochet notes in the softer dynamics.
VBT Ricochet without first finger on bow