How Often Adcenter Charge You?

I'm new in adcenter and reading FAQ I see that they charge you in case you reach 50$ or monthly. What about practice? Is anybody had experience with adcenter?
thanks

 

Hi Snookerok,

Microsoft adCenter periodically bills your account based on the charges that accrue. The amount at which adCenter bills your account is called the billing threshold. Over time, as you make timely payments, we will increase your billing threshold.

To determine your billing threshold, follow these steps:

1. Sign in to adCenter.
2. On the Accounts & Billing tab, click the Billing tab.
3. Select an account number and an activity period from the lists, and then click Go.
4. Your billing threshold will be displayed under your account name.

NOTE: There is no set period after which the billing threshold is raised. The billing threshold is automatically set by the billing system and cannot be manually adjusted. If your account has been declined three times at your current billing threshold, the billing threshold for your account will be reduced to the next lower level. You will always be billed when your billing threshold has been reached, regardless of your billing cycle day.

Thank you,

Brian H - MSFT