The Declipper enhancement adds amplitude peaks that were higher than the value and were therefore cut off when being imported into Nero WaveEditor.   
The following sliders are available: 
Detection Threshold

Specifies the volume at which removed amplitude peaks should be reattached.

Gain Modification

Reattaches the removed amplitude peaks. This percentage value should not be set too high because the peaks would otherwise be removed again after the file has been saved.