State law thus permits two types of UM coverage: (1) an excess policy which provides for UM insurance in excess of any available liability insurance (referred to as “add-on coverage”) and (2) a difference-in-limits policy which provides for UM coverage only for the amount of the difference between the available liability insurance and the limits of the insured's UM coverage (referred to as “reduced-by coverage”). Donovan v. State Farm Mut. Auto. Ins. Co., 765 S.E.2d 755, 757 (Ga.Ct.App. 2015) (internal citations omitted). As the Endorsement provides for reduced-by coverage, it seems compliant with Georgia law.