In case you don't find the field from the list, please enter the field ID instead. The input is made for both select and manual input. Please try that.
MB Blocks was created quite long after MB Conditional Logic, and so the MB Conditional Logic hasn't supported for MB Blocks yet. We're aware of this problem and working on a solution for that.
Did you mean by number of clones? If that, there's no built-in rule to do that. You might want to trigger your own JavaScript action at after_clone hook:
