Select this if you do not already have CHSBHC - BBP - Nude and Jiggly Mod by CherryHotaling and wish to use the UNPB BBP v2dot2 animations that are included with this mod.
The main difference is the walking animation. Not selecting this allows you to have no animations at all which seems to work best with smaller breasts as you still have a bounce without weird deformities.
The reason is UNPB BBP animations make UNP Normal and Skinny breasts flat when walking forward and the ones from CherryHotaling are better in this regard (but not perfect).
http://skyrim.nexusmods.com/mods/4888