Was your loader factory installed?
The confusion comes because there is a separate WSM for the loader and the tractor WSM does not address the loader.
The listed pressure for your tractor is 2480 to 2630 psi. Even with a loader, the pressures will be almost the same depending upon which comes first in the circuit, the 3 pt or the loader.
How many hoses on your loader valve. 6 or 7? I ask to figure out the hydraulic circuitry on your tractor. If there are 7 hoses, likely the loader valve feeds pressure to the rear of the tractor through a power beyond port.
Do you have rear remote(s)?
Adjusting a relief valve without knowing the hydraulic circuitry is not wise.
With a loader there will be more than one relief valve and one will affect what the other can do.
If you are very concerned you are not getting every available lb of performance from your loader, I would suggest you spend the $ to have a knowledgeable Kubota mechanic make any adjustment. It does not take long.
Dave