What Does This Mean Box._x = -1;

box._x = box._x + 1;

move the box x position equals itself and move 1 pixel if placed in an enterframe event ok i understand ........

box._x + = 1 ;

shorthand version i understand
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but

what does it mean if the symbol plus or minus is in front of the equals symbol rather than behind

box._x = - 1;


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