"i++" is an expression with a side effect. Though its side effect is to increase the value of i by one, its *value* is the value of i before the increment. And that is the value you assign to i (using "=") *after* the increment happened.
With other words: the increment does *not* happen after the whole assignment, but only after the subexpression "i++" got evaluated (to the value of i), and *before* the assignment.
Does that help?
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus