Net water, not tank rating. Use the Tank Volume calculator if you have not measured it.
RO/DI to add to bring salinity down, or salt to add to bring it up, without shocking anything.
Dilute slowly. Add the RO to the sump over hours, not minutes, and never pour it into the display. Salinity dropping fast is harder on corals and inverts than the high reading you are correcting.
RO to add = V × (S₀/S₁ − 1) = 284 × (36.50/35.00 − 1) = 12.2 L
Lowering salinity is conservation of salt. The salt already in the tank is fixed, so adding fresh water spreads it through a larger volume: S₁ = S₀ × V ÷ (V + added). Solve for the water to add and you get V × (S₀/S₁ − 1).
That formula raises the water level, which a full sump may not accommodate. The alternative is a swap: remove V × (1 − S₁/S₀) litres of tank water and replace it with the same volume of RO/DI. Same final salinity, same total volume.
Raising salinity is the salt mix calculation applied to the difference. Dissolve it in a bucket of tank water first, because dry salt hitting the sump raises alkalinity and pH locally enough to cause precipitation.
The gentlest way up is to stop topping off with RO and top off with mixed saltwater instead. Evaporation then concentrates the tank at exactly the rate it evaporates, which is slow and steady.
Speed matters more than the destination. Most reef livestock handles 33 to 36 ppt without complaint. What causes damage is moving through that range quickly. Hold changes to under 1 ppt a day and inverts will not notice.
Correct the cause as well as the reading. Salinity that drifted up means top off is not keeping pace, and salinity that drifted down usually means an ATO overshooting or a leak.
Sources: UNESCO EOS-80 / Millero & Poisson 1981 · Red Sea Salt manual (PDF)