Hi Ray.

Ok well Neale explination says it all really just went round the houses a bit. .Lol

Most standard steppers are indeed 200 steps per revolution. Which we can then break down into further Micro steps using the drives micros stepping capabiltys. So drives often come with preset micro stepping options. These are 200 which would be classed as full stepping Ie each pulse would move one full step. Then 400, 800, 1600, 2000, which could also be called 1x 2x 4x 8x 10x etc and beyond often upto 256x.
Now in reality there's no point going any higher than 10x(2000ms) as the motor can't resolve to much more than that. Also it it requires many more pulses from the parallel port so your putting stress on the computer for no gain.

If you set the drives to 1600 and then set the steps per to 1600/screw pitch then you won't have any issues with incorrect distance movement.