Update the docs too

docs/howto/bill.md

@@ -89,11 +89,16 @@ Currently this is the recommended way of retrieving the costs from GCP.
 1. Select 'Reports' on the left sidebar
 1. Under time range on the right sidebar, select 'Invoice Month'
 1. Select the time range you are interested in. Note that this has to be at least two months right now, or the next step does not work
-1. Under 'Group by', select 'Month -> Project'.
+1. Under 'Group by', select 'Month -> Project' or just 'Project' if the time range is only one month
 1. Under the chart, click the 'Download CSV' button.
+    ```{important}
+   It is important to not change the name of the file downloaded from GCP as it is used by the deployer to incur the month we are billing for.
+   ```
+
    ```{figure} ../images/gcp-billing-ui.png
    GCP billing UI
    ```
+
 1. Run the following deployer command to convert the generated CSV file into the format required for the invoicing process.
    
    ```bash