Why the values appear before i enter anything?

One Possibility - When you test individually, you might not have set test values for the rule inputs. But after combining them in the parent interface, you might have passed value to the rule inputs of the child interfaces.

This isn't well-published, but child interfaces will inherit the values of local variables set in parent interfaces when the local variables share the exact same name.  This of course goes away if the child interface properly scopes its own local variables of the same name, which is what you should be doing anyway.  Without seeing any of your code it's impossible to say whether this is the issue, but I suspect it might have something to do with it based on your description.