Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32n6/STM32N645/ETH/ETH_MACL3A31R#0x0
Layer3 address 3 filter 1 register
Layer 3 Address 3 Field
https://github.com/modm-io/cmsis-svd-stm32