There are three types of Accessible Parking Permits, you can check the eligibility on the Transport Victoria website.
Australian disability parking (ADP) permit for individuals
An ADP permit allows eligible permit holders to park a vehicle in an accessible parking bay for the time shown on the sign, or to park in a standard bay for twice as long as the time shown on the sign.
Australian disability parking (ADP) permit for organisations
An ADP for organisations permit allows the registered vehicle to park a vehicle in an accessible parking bay for the time shown on the sign, or to park in a standard bay for twice as long as the time shown on the sign.
Double time (DT) permits for individuals
A DT permit allows you, as a driver or passenger to park in a standard parking bay for double the time on the parking sign. It's a Victorian permit that can't be used interstate and does not allow you to park in accessible parking bays.