Hi Michael,
Generally Average CPC = Sum of costs/Sum of Clicks for that period of time.
So can you try calculating the total average CPC by the following method Sum of total costs(for those 7 days )/Sum of total clicks (for those 7 days ) instead of Sum of average CPC/No of days.
I hope it resolves your problem.
Thanks for your response@Dorian.
Cheers,
Raghavendra, AdWords API Team.