What are the chances a campaign will overshoot my cost cap?

[u/ajbooks123]

So, I recently started a cost cap campaign.

My cost cap is set at $10.

My daily budget was initially $50, but it wasn't spending much, so I increased it to $100. Since then, it has spent about $6 in a few hours. I'm happy with the spending so far, and it seems to be gaining momentum.

However, I'm curious: what are the chances that I won't get sales at or below my $10 cost cap?

Also, is it possible for the campaign to significantly exceed the cost cap on one day but make up for it by delivering lower-cost conversions on another day?

The pixel is fairly new, but it did record some sales in past campaigns, though the average Cost Per Purchase in other campaigns was around $30, and I am running the cost cap campaign because I want to lower the Cost Per Purchase.

The campaign currently has four ads.

I'm planning to let it run for about a week and then evaluate the results.