Each time a cashier changes a price at a register, it shows on the Price Challenge Verification, or PCV. The purpose of the PCV is to make sure that the items in question have the proper signing (or that the signs are in the right places). I'm not sure how one goes about clearing all the items, seeing as I've never actually done the PCV. The PCV is the responsibility of the LOD, but many ETLs like to delegate it to their underlings because it gets in the way of meal planning/social hour.
Note: when you're doing ad takedown, any sign that is Not Found will show on the next day's PCV so that the LOD can make sure the sign isn't still there. If you and the opening LOD get along, try to Not Found as seldom as possible.