How are you bottling? The beer will lose some CO2 on the way to the bottle, so typically you bump it up a bit. How much is a bit of trial and error until you dial in your system, but 2 psi is a good starting point. Also remember to vent the keg and just use a tiny bit of gas to push the beer into the bottle while filling or it will come out way too fast at the higher pressure. You want slow and gentle.