Hello amucci,
A Backup Job set to backup up 300GB of data and keep 2 copies on a schedule: Base: Wed & Sunday Incremental: Daily
With this schedule you will need, at the minimum, enough storage space for three Base Images and Incrementals.
The third Base image is created and verified before the oldest Base is purged. The keep 2 copy schedule with this amount of data would required about 1TB of storage (3 Base x 300GB plus ~100GB of incrementals).