I enjoy the chrony figures too. Nothing else involved with black powder is usually calibrated at all. The balls get shaved upon loading so each weighs differently, the chambers aren't uniform so no two are exactly alike, and the powder charges are measured by volume and not weighed so there's not any standards anywhere. But the figures do provide an accurate measurement of energy and are just plain fun. So sure the figures have meaning, as much meaning as calipers are useful for measuring any object. I never saw a seal of weights and measures on any measuring device unless it was used for some kind of consumer trade. I believe that most chrony readings are more true than they are false, and valid conclusions can be drawn from them with just a tiny grain of salt.