When you get into the main menu after start up of the game, at the bottom left is a number and letters.
The letters are the checksum. The number the currently installed patch.
This changes according to patch, but also changes when you play. So if you start a game and go back to the menu, it will be different than the first time.
The checksum that matters is always only the one, that's on display right after a fresh start of the game.