Wrong X coordinate in F3 (debug) menu

As you can see on the picture, I'm testing for a comand block in the coordinates below me, but it says it is air. I know, i can use relative coordinates, but I'm going to use these coordinates in a command block, far far away. The problem is not with the /testforblock command, because it appears to /setblock, too. It is the X coordinate, displayed by the debug menu. I have to enter another number. This is frustrating, if I'm working with more and more coordinates.

Best regards, Kova.