Chantal Shopify Guru here!
In your admin, you can view all the invoices for your store under Settings > Account in the Invoices and Fees section. When you click on the date of the invoice, it will show all the fees that are included on that invoice - including details for the specific apps.
The billing cycles for apps are each different since they start on the day that the app is installed on the store. We have a guide here that goes over rading your invoices as well as when the different fees become paybale.
Hope this helps!
Chantal, Shopify Guru