Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32f2/STM32F215/NVIC/IPR18#0x0
Interrupt Priority Register
IPR_N0
IPR_N1
IPR_N2
IPR_N3
https://github.com/modm-io/cmsis-svd-stm32