UrbanPro coins are deducted only when you respond to a student enquiry. The amount deducted is dependent on the category that the student is looking for the classes.
Coins are deducted as per your usage and you have the control over it.
Also, coins are automatically deducted for all the customized responses that you have set to be sent automatically. Please check Point 1.3.11 for further questions on how to set up customized responses to be sent on your behalf.