Just a minor typo for better README

[jelacicedin]

I would just change the README to state:

"SMD is made up by data from 28 different machines, and the 28 subsets should be trained and tested separately. For each of these subsets, we divide it into two parts of equal length for training and testing. We provide labels for whether a point is an anomaly and the dimensions that contribute to every anomaly."
It is a bit confusing otherwise :)