limitation of streams

NetBackup 5220/5230 Appliance is preconfigured with 8 streams in total for the appliance. In many cases this is not a limiting factor with the notable exception of Oracle backup where the number of streams can be very high.

I know that many factors and dependencies : from storage unit the maximum stream per drive is 2-32 can be configured for multi stream ,So how come if I used the Appliance ? max 8 streams

Please advice,,