Integer variables can only store integral values themselves. That's why they called that, obviously.
Result of any operation on integer is rounded so one could store it. For you that means that if you add too small value, no change will even happen at all. And on top of that, discarded decimal digits are not accumulated. So if you expect your integer to increase by 1 after you add 0.4 three times, you wrong: nothing will change because decimal part is always discarded.
That's a basics of integral types, actually. I am surprised you didn't knew that.