The final version of the documentation for Maya is still under construction. This temporary version is based on the Blender documentation, though its contents is relevant to Maya as well (both variants use the analogical UI).

Normalize Scale

The Normalize Scale functionality automatically scales selected islands before packing so that the average texel density is the same for every island. The process is called normalization. In order to use this option, enable the check box located in the Normalize Scale subpanel header:

Optionally you can also enable the Island Scale Multiplier option to specify scaling factors (multipliers) to be applied after normalization is done on a per-island basis. Using such multipliers you can prioritize islands i.e. assign multipliers larger than 100% for islands of higher priority (so that they will be scaled up after normalization) and/or assign multipliers less than 100% for islands of lower priority (so that they will be scaled down).

Multipliers are expressed as percentages, for example:

multiplier 100% means scaling by 1 (i.e. no scaling after normalization) - this is the default value for all islands
multiplier 200% means scaling by 2
multiplier 50% means scaling by 0.5 etc.