Help!

this is probably a silly question but why does the following work

b_mc.onRelease = function() {
numb–;
m_mc.p_mc.loadMovie(pics[numb]);

if (numb<=0) {
numb = 5;
}
};

and the following doesn’t

b_mc.onRelease = function() {
if (numb<=0) {
numb = 5;
}

numb–;
m_mc.p_mc.loadMovie(pics[numb]);
};

why is it that the condition works after the actoins have been peformed and not before.Still not found out why?