about the move and the coordinate system

i used EMC2 2.3 version, and a sherline CNC machine. the g code seemed to be very simple, but i just cannot image how it worked this way~!
e.g: i wrote "g01 z .14"(regardless of the units), i supposed the Z axis will move up, but to my surprise, it move down!! so i wondered if this is the matter of the coordinate system~~if it is, what should i do to make it move right, like the preview plot and control it freely~??

thanks ~~a billion~!

thx, i get it ~~when i configure the stepper motor, i success to do it~