Generally when launching a new campaign and set a low daily cap and you are flighted (your daily cap < spending potential), Google tends to go over your cap, sometimes by a good amount. Moving forward to the 2nd day, 3rd day, and so on of running the same campaign with the same daily cap, it will usually spend the amount you set your cap at.
So with your spend exceeding your cap, no big deal. If you are on a budget, then lower your cap the next few days by a few bucks to make back what you spent extra. To avoid this in the future if you really want, don't set your cap as high the first few days of the campaign and test the waters. Chances are you won't get your money back. This happens all the time and Google probably won't have time to talk to you about this long enough to give you a refund - unless your budget is over $20K a week, which I highly doubt.
bleedx2