Also completed shows all successful runs of the policy, so if it was targeted to test group previously but no longer is i think they show up in the successes even though it is no longer targeted to that group.
Another possibility is that if the machines existed in your organization prior to the existence of Casper Suite, they could've had the driver installed without the help of the policy.
@duffcalifornia - if that were the case - and I've seen that too - the numbers would be reversed. The "has xxx installed" would likely be higher than the "installed by Casper".
Looks like there was not a recon at the end of the policy, I'd guess.