Strictly speaking, it should be 5g per 100g of food, no matter how much you're eating (and no more than 15g fat per meal). If you did eat something higher than 5% in fat, but in a smaller quanity, you'd be taking a chance with side effects.
It's to do with the concentration of fat in your food, as well as the total amount per meal.
I'd start off on the cautious side until you get used to the tablets, then you can experiment and see what you can get away with (or not!)