When using the PMIX Mapping screen in preparation for analyzing theoretical usage (Accounting > PMIX Mapping), 'scales' are used to connect the pour sizes of beer, wine, liquor to the POS buttons used for those products. The same idea can be applied to Soda BIBs, and those numbers are also shown below.
NOTE: For sales of wine by the bottle or beer by the bottle, you will use a scale of '1' assuming the product has been setup with inventory unit of 'bottle'. Scales other than '1' are for beer and wine (and liquor) by the glass.
These numbers can also be viewed on this google spreadsheet.
See this article for some real work examples of how to use this data: Some Examples of PMIX Mapping Scales
Pour Size v Scale Calculations
For the same data as above, but in a format that allows you to copy and paste scales, use this Google Spreadsheet or you can download the attached Excel file.