Scales for PMIX Mapping determine how much of a product we report as being sold for each POS button-push.
Let's look at some examples:
Above is a restaurant that sells the same wine (Echo Bay Sauvignon Blanc) by the bottle and by the glass. They've mapped the same bottle to each of these buttons (which is correct, as this is the same product that will be used). But each glass of wine uses only 6 fl ounces where a bottle sale uses the whole bottle. Accordingly, the scale for the bottle is set to 1 (each time a bottle of wine is sold report 1 bottle x 1 is sold) and the scale for glass is set to 0.236588 (6 fl oz / 25.36 fl oz).
Ok, now, let's use an example of a scale greater than one.
The above restaurant sells 6 packs of beer. In this case, you would map the product "Blue Moon Belgian White 12oz Bottle" which has a unit of 1 bottle. Since each time this button has been pushed, 6 bottles are sold, we'd set the scale to 6 and each time the button is pressed, 6 bottles of Blue Moon will be reported as sold.
Thus far all the examples have been of Products, but the same logic applies to Recipes as well.
So for example, above are two sizes of Fries large & small, there the same Recipe has been mapped to both large and small fries and the scale is just set for double the value for the large fries to account for the additional fries being sold.