Once I have the ADE, what equation do I used to determine the MACO

In the past, either 1/1000th of the lowest therapeutic dose or 10 ppm was used as the dose in the maximum allowable carryover (MACO) equation. Now that there are acceptable daily exposure (ADE) values the MACO equation must be slightly modified. Using the ADE (analogous to PDE) is simply a matter of replacing the "Lowest Dose (A)/Safety Factor" with the ADE value in the standard maximum allowable carryover (MACO) equation.

Therefore, the new equation will look like this:

Source: Walsh, A. (2011).  Cleaning Validation for the 21st Century: Acceptance Limits for Active Pharmaceutical Ingredients (APIs): Part II