The target impedance of the SERDES_x_VDDAIO pin is calculated as 240 mΩ, based on the following values (see Power Supply):
Ripple = 5%
The following figure shows the impedance of the plane (SERDES_x_VDDAIO) improved by the decoupling capacitors. The impedance of the plane is kept under 0.2 Ω till 100 MHz.