You weren't expecting to get pulled over when you were out for the night. The policeman who stopped you claimed that you had been driving erratically, but you didn't think that was the truth. Despite that, you listened as they said what they needed to and even gave them a breath sample willingly.
What you were surprised to find out is that your blood alcohol concentration was at .06%, even though you'd stopped drinking a few hours ago. Still, the legal limit is .08%, so you're safe against penalties, right?