You could go from 1.023 to 1.025 within a period of 24 hrs. The goal would be to raise the specific gravity very slowly. Raising specific gravity too quickly would be very stressful on fish, pods, snails, crabs, invertebrates, corals, etc.
You may also want to check out various published articles on hyposalinity treatment, which involves lowering and raising specific gravity to treat fish infected with marine ich in QT.