Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f7/STM32F730/SDMMC1/FIFOCNT#0x0
FIFO counter register
Remaining number of words to be written to or read from the FIFO
https://github.com/modm-io/cmsis-svd-stm32