Most food labeling in the US is done this way. Gross measures (total volume, weight, etc) are in imperial while the nutrition facts are in metric. So milk will say, serving size 12 Oz, protein XX g.
Both net contents and serving size include metric measures.
"Food labels printed must show the net contents in both metric (grams, kilograms, milliliters, liters) and U.S. Customary System (ounces, pounds, fluid ounces) terms." [0]
"The serving size is expressed as a common household measure followed by the equivalent metric quantity in parenthesis." [1]
[0] https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocument...
[1] https://www.fda.gov/Food/GuidanceRegulation/GuidanceDocument...
For example, I have two yogurts, one has 18g carbs per 170g serving, the other has 34 g per 227g serving. Quick, how much more carbs would I have if I ate the same amount?
It's a lot easier to tell if you know one is 6oz and the other is 8oz, or if the servings were designed in metric sizes (e.g. 150g and 200g).