A Z step is the amount of steps (wiki stepper motors) it takes to raise the Z axis 1 mm. This is all mathy with the diameter of the rod and pitch of the screw (you have 8mm rods). The answer to Z steps is 2560 only. Unless you change rods. An E step is the amount of steps it takes to turn the hobbed bolt enough to move the filament 1 mm. That is NOT to extrude 1mm of filament. to move the solid unfettered 1.75mm cold filament 1mm. This number is like... 723 or something from factory. Having this out of whack will cause you to have trouble "overfilling" layers, splitting layers, clogging on the first layer, dragging, gooey nonsense, oversize parts etc. You can VIEW AND EDIT your steps in the EEPROM. This is for "fun" only. They will reset to firmware norms when you power off and on. You can find EEPROM viewer in most software front ends. To permanently modify E steps (again... do not modify Z steps, they are hard 2560) you need to modify the firmware in the arduino IDE. http://help.robo3dprinter.com/Wiki/RoBo_3D_Firmware to calculate your extrusion, you can do a LOT of trial and error.. or.. do some maths http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide there's a calculator out there that can math for you. Its got strange nomenclature though. The picture is of the line in the code that tells the machine what each axis uses for its steps. the last one is extruder steps.