For non-Russians, these are the steps:
1) Think of any two-digit number (e.g.: 54)
2) Subtract from it its composing digits (54 - 5 - 4 = 45)
3) In the chart, find the number you get and note the character next to it.
4) Click on the square above the chart, that character will appear in it.
Your mission, should you choose to accept it, is -- without looking at the comments -- to figure out how this works. If you do, you get to go on a free trip to North Korea.