1.6.3. Using the Correct Number of Power/Ground Via Pairs and Layer Number
Unless you change manually, the PDN Tool initially sets all power groups to the same Layer Number . For this example it is 18. You must change this to match your PCB design.
Long vias between the plane and FPGA have higher vertical loop inductance than short vias. The planes placed farther from the FPGA have higher loop inductance. Because inductance impedes high-frequency current delivery, it reduces the effective maximum frequency of the PDN. To reduce loop inductance, you can place planes closer to the FPGA.