Dear Green Lace,
there have been minor changes between 2017.2 (the version with which the tutorial was done) and 2017.12 related to the precise way in which the mobility is evaluated, which results in a tiny change of the exact value of the calculated mobility. Unfortunately, the calculation of the mobility is a very subtle calculation, and even small changes in the code, or running on different machines, result in slightly different calculated values.
However, I would not be concerned, as the results are in the same order of magnitude. This is the most important point, and indicates that your have done the tutorial correctly. Congratulations
I hope this solves your doubts.
Regards,
Daniele