Why do you want to get the checksum information?
Project type is Bootloader Project. I find out that this is the reason why hex file has changed on two different places. Looks like that the "second place" is bootloader "checksum".
I couldn't find any info about "bootloader checksum", is it possible to get any details about it (checksum calculation, location in hex file...)?
Your understanding is right.
Because in hex file, every line will make checksum. the second different is the line checksum.
How to do the checksum:
The last byte in the line is the checksum byte.