I recently did some delving into the math of the game trying to figure out exactly how all gold bonuses were calculated. I can say for sure that most numbers in the game are not whole numbers, they have decimal places which are sometimes not shown at all (the decimal is dropped) and sometimes rounded off, so a 64.8 internally can show as 64. His bulls stats which show as 64, 65 and 81 are very likely, internally, something like 64.7, 65.8 and 81.4, which when added and divided by three, and then rounded, is 71.
It was absolutely maddening trying to figure out how the numbers worked. Because once I realized there were unshown decimals and the numbers were being rounded (0-.4 rounded down, .5 and up rounded up), other numbers stopped working… until I realized that some just have the decimal dropped when displayed, but retain the fractional part for any math.
Of course, this is just an educated guess, based on the math I did to figure out how and where gold bonuses were applying in the new explores.