Symantec Backup Exec System Recovery: Performance slider in Progress and Performance tab can NOT be set to slow by default

Application: Symantec Backup Exec System Recovery 8.5 Server editionVersion: 8.5.5.33937

The performance slider in Progress and Performance currently is set to Fast by default. We have overnight backup job running & we would like to set this slider to slow, but the Backup Exec currently is not letting this to happen. May i request, to allow us to set thiswhen setting a backup job??