Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/Keil/AT32F405xx_v2/USB_OTGFS_GLOBAL/GRXFSIZ#0x0
OTGFS Receive FIFO size register (OTGFS_GRXFSIZ)
RxFIFO depth
https://github.com/cmsis-svd/cmsis-svd-data