It is a complex mathematical algorithm, that defines any Alpha Irish male's exponential decay of standard for a female companion for the night. The two variables of this algorithms are,
1) how much Guinness he had so far &
2) what time of the night it is.
JB Standart has a inverse exponentially proportional relation with these two variables. As night goes on, and the more he has to drink; the lower his standard gets.
John: Yo Milton, what's the JB Standard for her
Milton: 3 Guinness down by 9, she will be a 9.