Calibration

Currently there is no way to pull the data in from the Eprom.

You have two options and it depends on what you want to do
download the config.h file Coby (one of the Robo guys) modify it and reupload the the new firmware with your adjustment to the steps settings located in the config.h file
--or--
modify it inside of repetier host as add on gcode that is added to the beginning of each gcode print
this only if you are using slic3r
go into the configuration of slic3r
under printer settings
under Custom G-Code
in the start Gcode box you can add something like this

M215 X 79.107 ; SET X steps
M215 Y 78.953 ; SET Y steps
M215 Z 2207.657 ; SET Z steps

M215 is the Gcode command to adjust the steps of the stepper motors

you formula is simple cross multiplication

your current steps per inch ||||| your new steps per inch
------------------------------- ||=|| ---------------------------
you current measured value |||||your desired value


as an example
79.400 is the current steps for x and the x distance was 40.5

79.400 ||||| 78.419
-------- ||=|| ---------
40.5 |||||| 40

or 79.400 * 40 / 40.5 = 78.419
M215 X 78.419 ; SET X steps


REMEMBER that these are only formula based approximations and that yo may have to do it several times to fine tune it exactly
AND
The x and y probably are not going to be the same so don't just put it the x values for y
AND
Case is important in GCODE so use it as you see here

I also keep it to 3 digits to the right of the decimal no more no less

If you choose the firmware route the formulas are the same it is simple a more permanent way of doing it but just takes a lot longer to do

There is also one for the the extruder but you probably are not going to play with that one much
M215 Exxx.xxx