I believe those percentages are the percentage of RDI (recommended daily intake). It's not saying protein is 48% of the calories or the weight. It's saying the protein is 48% of the protein you should eat in a day.
Now RDI are not tuned to low carb eating so you can ignore that and use macros from carbmanager, myfitnesspal, or any other tracking app. But a "napkin calculation" is, fat has twice as many calories as protein. So here they are more or less equal, so that's roughly 2 parts fat and 1 part protein, or 67 and 33% respectively. Hope that makes sense.