What the table does
This table only appears when Boost Control Mode is Closed Loop. Each cell is the boost pressure you want the ECU to hold. The controller then adjusts solenoid duty to reach it, starting from the closed loop base duty table. The axes are yours to choose, and you can map it in up to four dimensions, so the target can depend on RPM, gear, a switch position or other channels at once.
Using it with a trim module
A common setup puts a rotary trim module on one axis so the driver can pick a boost level from the cabin. For example, you might build three levels: a low setting for wet roads, a street setting, and a higher track setting that adds a little more boost only at high RPM, where the engine and turbo can use it safely. Each level is just a row of targets, and the base duty table needs a matching row so closed loop only has a small error to correct.
Keep your targets within what the wastegate, MAP sensor and fuel system can support, and check that each target is actually achieved in logs before raising it.
For the whole setup see boost control, and to adjust targets by gear or temperature, boost corrections.
