There are two settings that can be configured in regards to OneDrive storage, as shown in the following screenshot:

The Default storage in GB setting controls the default allocation for new OneDrive for Business sites. It has no impact on existing sites. Though the actual size of your OneDrive for Business site can be expanded (depending on your subscription), the maximum initial size is 5 TB. The default is 1 TB. If you assign a default size larger than a user is licensed for, their site will be rounded down to their licensed amount. The minimum size you can configure is 1 GB.

You can also use the following PowerShell command to manage the initial storage setting:

Set-SPOTenant -OneDriveStorageQuota <Size in MB>

The value for Days to retain files in OneDrive after a user account is marked for deletion governs how long a OneDrive site will be accessible. It is not the same as a Retention Policy (formerly called a Preservation Policy), which stores deleted items in the Preservation Hold Library. The minimum value for this setting is 30 days while the maximum value is 3,650 days (10 years).