Another way to explain the modulus operator is like this, in a not-so-decent coding method:

Code:

---

function get_remainder(number, value)
{
	temp = int(number/value);
	return(number-value*time);
}

function another_function(parameters)
{
	some_var = 160;
	// ... more code above here
	some_var = get_remainder(some_var, 30); // returns 10 and the same as
	// some_var %= 30; // also returns 10
	// ... more code below here
}

---

Although code like this is meaningless, this is the basic algorithm behind it - it's not all that complex either.