Normalization by percent

[l-w-c]

Some video encoders allow you to normalize by percent (e.g. TMPGEnc and DGMPGDec).

As normalization in those softwares must be between 0%-100%, can you please explain:
1) What percent of Normalize should be chosen if the initial volume is too low?
1) What percent of Normalize should be chosen if the initial volume is too high?

Thanks!