Using the panel on the left side, the user specifies the values of/for the context variables required to match the rule.
When you enter the values of something, you enter value for it, or you enter the value of it?
I think that if those variables already have values, then those values are of the variables. If the variables have indeterminate values to begin with, and the user is supposed to enter something, which will be independently validated, perhaps, then those values are for the variables.
So, I vote for for in this case.