Becker's formula  =

(360/pay period - discount period) x (discount %/100 - discount %)

I noticed Wiley had some questions where they paid after the discount period date. 

For example, 3/10 net 30 and the company pays on the 35th day.  wiley used 35-10 for pay period minus discount period. 

Becker did not have any questions where they paid after the discount period.  So do we use the date when it was paid in the formula or discount date which would be the 30 days if paid after the discount period?