I've always (well sometimes)wondered how D&Ders calibrate all their numbers.
Clearly you did not
waste time enlighten yourself reading back issues of Dragon magazine, back in the day. Many were the debates over the mad rigors of calculating damage and other figures.
Unfortunately the OP left out much critical information. What was the cow's THAC0? Was it wearing the +1 Cowbell of Accuracy? Did the dwarf fail his Saving Throw against Alerting Livestock? Was he on a stool? (Because, y'know, it's hard to tip a cow from the bottom.)