If you have a mixed subscription, the storage will be implemented as per the subscription.

For example, if you have 10 Licenses of Google Workspace Business Starter (10X30GB=300GB), here you can assign 300GB pooled storage to the users under Google Workspace Business Starter as per your requirement.

If you have 10 Licenses of Google Workspace Business Standard (5X2TB=10TB), here you can assign 10TB pooled storage to the users under Google Workspace Business Standard as per your requirement.

Here, your Domain’s pooled storage will not be calculated as 10300GB due to the Mixed sunbscriptions.