I am not sure I understand the question. In the Flash Memory Map is a set of sliders. You can slide them back and forth. The S/W ensures that you do not go over 4MB. You must, of course remember the following:
NVRAM takes up 64KB. This is non-negotiable.
The boot loader (unless modified) takes up 64KB. This is non-negotiable.
If you do not want a backup image, set it to 0.
I believe by default, any FLASH space NOT taken up by the application, the bootloader, the backup image, NVRAM is given to the file system.
Yes I had not used the slider in a while. As you increase the size of the file system, the slider decreases the size of unused space, up to the 4MB limit. Further you are correct that ultimately, the slider updates the file customize.ldr. You have the option of directly updating customize.ldr, but we recommend using the slider.
The output from the build tells you the size of the application and the backup application. So,
MAX_FLASH_file_system_size = (Total_FLASH_space - (bootloader_size + NVRAM_size, + application_image_size + backup_image_size))
Using the sliders minimum value is 64K you said that if no backup image is desired
(I would read something about how backup image can be used do you have a document?)
I could set it to 0 but as I said min with sliders is 64K can i safely write BACKUP_RECOVERY_MAX_SIZE_IN_FLASH 0 ? or it has to be 64K
Compressed Image Size: 641705 the closest value I can get is 760000
that is the size I have to use for application image?
The backup image is used by the bootloader in cases where your primary application becomes corrupt. Before running the primary image the bootloader calculates a CRC for the image. if the CRC does not agree with the CRC in the header, the image is considered corrupt. IN that case, the backup image is run. Generally you want the backup image include the FTP server, so you can reload your primary image. It is optional.
I believe in customer.ldr you can set the size of the backup image to 0, assuming that is what you want. What you do with this is application specific.
I believe the answer is similar for the application size. It is possible that the granularity in using the sliders is large. To set sizes with a finer granularity directly update customize.ldr.