"If distracting thoughts arise, acknowledge them..."

I know I am supposed to let distracting thoughts pass, but how? I am sitting daily, and doing well on putting in time, but the quality is....?

For example, I had a snafu with my auto company when they did not receive my check last week. I canceled the check, and it showed up the next day at the financing company. It was a minor irritation, the payment is not due for several weeks, so there is nothing to stress about, but during zazen this morning I kept wondering why the check was late? Should I send another one this week or wait for next week? Why did it take so long to arrive? Etc...?

I understand that thoughts will come up, but how do you acknowledge and let them pass by?