Internet traffic is like an ocean. Some days, there will be small waves. Other days, there will be great big ones. So, sometimes your ads don't get much clicks because of low traffic, but your monthly budget allow your ads to get more clicks on certain days when traffic's higher.
That's why we cater up to 10% budget buffer than your average monthly budget allows for clicks and conversions. This is called overdelivery. And it's a good thing: if you end up getting too much clicks or conversions -- to the point where you accrue extra costs more than 10% of your average monthly budget -- we'll give you those clicks or conversions for free.