Answer
About 15,000 failed requests. In review, anything from 10,000 to 22,500 counts as right.
The worked estimate
30 days × 1,000,000 = 30,000,000 requests. The budget is 0.05% of them: 30,000,000 × 0.0005 = 15,000 failed requests. When the budget is spent, teams slow down risky changes until it recovers.
Numbers: Numbers to know.