When I use Instant3D and I have a mid-planarity somewhere inmy part, the ruler doubles the increase of my dimension!

I happened to stumble across this by accident and I'm glad I did,before I used I3D to much.
Is this normal behaviour?

Some screenshots for clarity:

Instant3DBefore Manipulation

Instant3DDuring Manipulation

Instant3D After Manipulation

Instant3D Blind Feature Is Not Affected

Instant3D Blind Feature Is Not Affected 2

Instant3D Underlying Sketch Is A Centre Rectangle

Notice the blind feature dimension is not affected, further puttingthe blame on mid plane or symmetric doodads.SolidworksParts And Features