Bioequivalence and Bioavailability Forum

As per FDA guidance for potassium chloride and citrate BE studies, we have to collect urine at specific time intervals (8 intervals - 0-1, 1-2, 2-4, 4-6, 6-8, 8-12, 12-16 and 16-24) for 2 days and do baseline correction of post dose samples, taking the average of 2 baseline days.
I have a doubt on this baseline correction.

1. Do we have to take the 24 hrs urine potassium (mg/ml) for 2 days and taking the average of these two values, subtracting the post dose values with the average baseline value? In this method, the baseline correction will be period and subject specific but not time point specific.
   or
   
2. Do we need to take average of any one time interval of two days and subtract the post dose value of a particular time interval with the interval specific baseline value? In this method, the correction will be period, subject and time point specific.

Could you please help to clarify the doubt?