When restoring,does "processed" refer to db or backup size?

Got a 1TB database that is currently being restored.

The backup is a replica of the actual database, so nothing is down, but restore has been running for 2hrs and RedGate says it has processed 120GB so far.

Is that 120GB against the backup size (~240GB) or it does refer to the 1TB database size?

I need to know so I can calculate how long would it take and if I have to stop the process and start early morning instead.