The follow map will converter "Left Ctrl + 1" to "1" and "1" to "2". 

It means when you press "1", key "2" will be typed. 

When you press "Left Ctrl + 1", the original key "1" will be typed.

If you press "Shift + Left Ctrl + 1", the character "!" will be shown.

If you press "Shift + 1", the character "@" will be shown.

It seems that key "1"  is "2" now. but "Left Ctrl + 1" will still be "1";

(This example is based on QWERTY keyboard.)