Yesterday I changed my budget from 50 dollars/day to 25 dollars/day, but today I found the cost is 36.35 during the last few hours. Why is that? why the cost exceeded my budget?
you cost may vary on a day to day basis but over the month should average out and balance your daily budget settings.
you need to observe it for week and see what happens. I feel this shouldn't happen. Perhaps it was your first day of change and you changed the budget in the middle of the day? Did you try contacting google?