This one's pretty obvious; somebody else must have seen this:
Okay, remember when Vassili (Jude Law) does his incredible shooting scene, just after meeting Danilov (Joseph Fiennes) in the fountain?
Danilov: "Do you know how to shoot?
Vassili: "A little."
So, he knocks off a bunch (5) of Germans in a row.
Fast forward to the scene where Danilov/Fiennes is showing Vassili/Law the poster/article they are doing up to propagadize the feat, the scene where they are actually printing off the posters for the first time.
Here's the slip up:
If you take a look, the posters coming out of the machine have 4 big X's on them, representing kills. You can see it pretty clearly.
BUT, when Danilov/Fiennes takes one from the pile and hands it directly to Vassili/Law, it magically now has 5 big X's.
The ability to see. The ability to count.