Not all licences count towards your file storage limits. The calculations according to the documentation are as follows:
File Storage Contact Manager, Group, Professional, Enterprise,
Performance, and Unlimited Editions are allocated 10 GB of file
storage per org. Essentials edition is allocated 1 GB of file storage
per org.
Orgs are allocated additional file storage based on the number of
standard user licenses. In Enterprise, Performance, and Unlimited
Editions, orgs are allocated 2 GB of file storage per user license.
Contact Manager, Group, Professional Edition orgs are allocated 612 MB
per standard user license, which includes 100 MB per user license plus
512 MB per license for the Salesforce CRM Content feature license. An
org with fewer than 10 users will receive a total of 1 GB of per-user
file storage rather than 100 MB per user license.
Each Salesforce CRM Content feature license provides an additional 512
MB of file storage, whether Salesforce CRM Content is enabled or not.
File storage and data storage are calculated asynchronously, so if you
import or add a large number of records or files, the change in your
org’s storage usage isn’t reflected immediately.
The minimum values apply to Salesforce and Salesforce Platform user
licenses. If your org uses custom user licenses, contact Salesforce to
determine your exact storage amount.
Next to that your company can also buy extra storage.
If you have questions about this subject it may be easier to contact your Salesforce Account Manager.
