Affect

These options decide which components of owner are affected and how should it be affected.

"+X" means it will takes the target scale vector's X component, and apply on owner; "-X" means it will applies the negated target scale vector's X component to owner;

e.g.: if you only switch on "+X" & "+Z", then the owner will take target's scale vector's X & Z component, and ignore Y component from target completely.

Offset

The owner doesn't have to be strictly has the same value with the target;

if "Offset" is enabled, then the the specified Vector3 value is added to result scale at last;

Space Mapping

"Target Space" decides how to extract scale info from target, "world" means using transform.lossyScale, "self" means using transform.localScale;

"Owner Space" decides how to apply result vector to owner, "self" means using transform.localScale, "world" means using transform.localScale ="specified value" / "owner.parent.lossyScale";