I also have this same question, and I'm wondering if the previous response might be a case of double counting?
The number in box 1a (ordinary = nonqualified + qualified) includes the amount in box 1b (qualified), whereas the percentages were described "Fgn Source Inc Tot." 90.34% and "Fgn Source Inc Qual" 64.50%.
Which leads to think applying 90.34% to the total dividend amount is the correct answer.
