Cortex XDR Pro allows firewalls to send in logs for analysis and this requires 'x' ammount of 1TB units to be purchased.
PAN-XDR-ADV-TB - Where each license adheres to a) Allows ingesting up to 1 TB per month and no more than 33GB per day. b) Enables storing 1TB of data.
PAN-XDR-RTN-TB - For retention enforcement, each license allows the storage of 1TB of data.
For example, suppose you need 14 TB of log storage for long term retention but you only need to ingest 2TB per month.
You would get
2 x PAN-XDR-ADV-TB
12 x PAN-XDR-RTN-TB