Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/STMicroelectronics/STM32F7x/OTG_FS_GLOBAL/OTG_FS_GRXFSIZ#0x0
OTG_FS Receive FIFO size register (OTG_FS_GRXFSIZ)
RxFIFO depth
https://github.com/cmsis-svd/cmsis-svd-data