question about steps per unit

I’m looking at the marlin firmware on my lulzbot mini and trying to figure out how the x and y axes are using 100.5 steps per unit.

I can understand if it was 100 where I have a 200 steps per revolution, 16 microsteps and a 16 tooth belt.
However, I don’t see how it ends up being 100.5. Any hints?



Actually I just got an answer on #reprap. They add the .5 for shrinkage.

The extra 0.5 steps is there to account for the thermoplastic shrinking. We’ve used that fudge value on all our 3D printers for the X and Y axis. It’s served us well.