How to change the width of this part?

Hi

I've been given this part where all dimensions appear to be defined. I'm trying to change the width, but I can't seem to find the dimension for width:

Does anyone know how the width can be changed? Another question is, how are each points actually defined? Most of the points can't be changed but they appear to be defined. I can only see 3 dimensions in the entire part.

Thanks

SolidworksParts And Features