Amount of Space Needed for Dash Copy Backups Using Front End Capacity and Usage Reports

The stuff in the Deduplication documentation does not really make clear what we may need. We had Dash Copies a couple years ago and ran out of space then we migrated our backups to Hyperscale-X. Now that we are getting ready to setup Dash Copy work again need to get at least idea of what we need space wise as a best practice. BTW were on Prem not the CLOUD.