Set the values you want to apply, then click on Move, Scale or Rotate to transform all unlocked flattened shells. If Local is ticked, the scales and rotates will pivot around the center of each individual shell, otherwise the origin (i.e. u=0, v=0) is used. Use the Invert button to invert all values so you can quickly transform shells back to where they were, and the Reset button resets the field values back to their defaults.

Rescale U & V 

Use these buttons if you want to rescale shells so that their size in UV matches that in 3D. For example, if you load an OBJ with existing UVs and some shells are red and others are blue, clicking on the & button will rescale each of them up or down until they are closer to green in shading. Click on the U or V buttons if you only want to scale in that direction. As with the other transform buttons above, the rescale will only affect unlocked flattened shells.