Is it a bug in function Bootloader_Erase()? about stm32-bootloader HOT 3 CLOSED

bool bootLoaderEraseFlash(void)
{
    /**
     * @brief 定义FLASH每个Bank有多少Pages
     *        STM32L4系列分为两个Bank,每个Bank=256Pages 每个Page=2K
     */
    uint32_t numberOfPages = 0;
    uint32_t pageError = 0;

    FLASH_EraseInitTypeDef flashEraseInit;
    HAL_StatusTypeDef halStatus = HAL_OK;

    HAL_FLASH_Unlock();

    numberOfPages = (FLASH_BASE+FLASH_SIZE-USR_APP_ADDRESS)/FLASH_PAGE_SIZE;

    flashEraseInit.Banks     = FLASH_BANK_1;                                        // 擦除指定的Bank 目前用的L476RC只有一个Bank
    flashEraseInit.NbPages   = numberOfPages % (FLASH_BANK_SIZE/FLASH_PAGE_SIZE);   // 一次性擦除多少页
    flashEraseInit.Page      = (USR_APP_ADDRESS-FLASH_BASE)/FLASH_PAGE_SIZE;        // 擦除的起始页,从除去BootLoader开始
    flashEraseInit.TypeErase = FLASH_TYPEERASE_PAGES;                               // 擦除类型是“Page Erase”

    halStatus = HAL_FLASHEx_Erase(&flashEraseInit, &pageError);

    if ((halStatus == HAL_OK)&&(numberOfPages > (FLASH_BANK_SIZE/FLASH_PAGE_SIZE)))
    {
        flashEraseInit.Banks     = FLASH_BANK_2;
        flashEraseInit.NbPages   = numberOfPages - flashEraseInit.NbPages;          // 减去上次擦除的Pages得到剩余的
        flashEraseInit.Page      = USR_APP_ADDRESS-(FLASH_BASE+FLASH_BANK_SIZE)/FLASH_PAGE_SIZE;
        flashEraseInit.TypeErase = FLASH_TYPEERASE_PAGES;

        halStatus = HAL_FLASHEx_Erase(&flashEraseInit, &pageError);
    }
    HAL_FLASH_Lock();

    if (halStatus == HAL_OK)
    {
        logInfo("IAP Erase the flash [0x%08X-0x%08X] successfully!", USR_APP_ADDRESS, FLASH_SIZE);

        return true;
    }
    else
    {
        logError("IAP Erase the flash error!");
        return false;
    }
}