ZodiacPress uses GeoNames webservices to get birth place latitude/longitude coordinates and the timezone ID. Every time the ZodiacPress form is filled out and submitted, it accesses the GeoNames geographical database through its webservices.
GeoNames imposes a limit to how many times it can be accessed. They measure usage by “credits.” Free GeoNames accounts are limited to 30,000 credits per day, per username. They are also limited to 2,000 credits per hour, per username.
The ZodiacPress birth report form uses at least 2 credits every time the form is submitted. (That is one credit for looking up the city coordinates, and one credit for looking up the timezone ID. If the user types another city, that uses more credits.)
So, with GeoNames limits, that means that the form will work a maximum of 1,000 times per hour, and a maximum of 15,000 times per day.
This is okay for many websites, but if your website gets more traffic than that, you will need to purchase credits for GeoNames Premium Webservices.
GeoNames allows you to purchase credits for GeoNames Premium Webservices so that your form can handle more traffic. This also comes with added benefits which you can see on their page.
(If you do happen to get a Premium GeoNames account, then you should take advantage of Enhanced GeoNames.)