If you have a subVI that prompts for a number, it needs a numeric output connector so the entered value is avialiable in the calling program later. It seems that so far, your dialog subVI only contains a control, which can only be an input connector.
Create an indicator for your input and assign it to the output connector.
I don't think your question is very clear. Why don't you attach a simple example of your problem, it would help tremendously?
🙂