Sorry Slovenec for that ambiguous answer...

For your machine, the way I understand it, your "encoder count" is 10k. The "steps per mm" is 10k / 5mm = 2000.

So your calculation is correct... Are you sure there is no reduction in the gears that connect the servo to the ball screw? It is common to have a 2:1 reduction. If this is true of your machine then your "steps per mm" number will need to be 10k / 2.5mm = 4000

Mike