The checksum is a four-letter code which is procedurally generated by the game, representing the exact size of all your game files. If your checksum and my checksum are the same, then we have exactly the same files. Where this becomes useful is as a shorthand to determine whether there are any differences...if we say "the checksum with the mod is ABCD" and your checksum happens to be ABTY, then you know there's something wrong: you have extra files somewhere, made some changes, or didn't download/install correctly.
To find the current checksum for the mod, check the
download thread -- it will be listed by "Current Checksum" at the bottom of the first post.
To find out what your checksum is:
The
vanilla checksum is located in the launcher:
So the vanilla checksum with the 2.4.3 patch should be WIUP.
Then, after starting the game with the mod installed, you'll see a
mod checksum in the lower left of the title page:
Thus the mod checksum is CQCJ.
When reporting issues, it's always best to say "I have checksum CQCJ" or just "CQCJ", as a way of letting us know you have the exact files we'd expect for the mod. If you don't, and know why (let's say you made some changes of your own, or mixed in another mod), you absolutely need to say so.