Update understand-reservation-charges-postgresql.md

fix "an PostgreSQL" per Acrolinx

Author: jborsecnik

articles/cost-management-billing/reservations/understand-reservation-charges-postgresql.md

@@ -23,7 +23,7 @@ Stopped resources are billed and continue to use reservation hours. Deallocate o
 
 ## Discount applied to Azure Database for PostgreSQL Single server
 
-The Azure Database for PostgreSQL Single server reserved capacity discount is applied to running your PostgreSQL Single server on an hourly basis. The reservation that you buy is matched to the compute usage emitted by the running Azure Database for PostgreSQL Single server. For PostgreSQL Single servers that don't run the full hour, the reservation is automatically applied to other Azure Database for PostgreSQL Single server matching the reservation attributes. The discount can apply to Azure Database for PostgreSQL Single servers that are running concurrently. If you don't have an PostgreSQL Single server that run for the full hour that matches the reservation attributes, you don't get the full benefit of the reservation discount for that hour.
+The Azure Database for PostgreSQL Single server reserved capacity discount is applied to running your PostgreSQL Single server on an hourly basis. The reservation that you buy is matched to the compute usage emitted by the running Azure Database for PostgreSQL Single server. For PostgreSQL Single servers that don't run the full hour, the reservation is automatically applied to other Azure Database for PostgreSQL Single server matching the reservation attributes. The discount can apply to Azure Database for PostgreSQL Single servers that are running concurrently. If you don't have a PostgreSQL Single server that run for the full hour that matches the reservation attributes, you don't get the full benefit of the reservation discount for that hour.
 
 The following examples show how the Azure Database for PostgreSQL Single server reserved capacity discount applies depending on the number of cores you bought, and when they're running.
 
@@ -41,4 +41,4 @@ To understand and view the application of your Azure Reservations in billing usa
 
 ## Next steps
 
-If you have questions or need help, [create a support request](https://go.microsoft.com/fwlink/?linkid=2083458).
+If you have questions or need help, [create a support request](https://go.microsoft.com/fwlink/?linkid=2083458).