System Workbench for STM32

I found assembly code stm32h7x.S is actually setting PG bit as following.

define STM32_CR_PROG 0x00000032 /* PSIZE64 | PG */
// ...
mov r6, #STM32_CR_PROG
str r6, r4, #STM32_FLASH_CR_OFFSET

I'm confused.

I'm waiting for an analysis by specialists.

Regards,
Atsushi