The brief explanation of SOS (which starts at the top of the blog post) uses a toy dataset. This toy dataset has 6 data points. Each data point has two features

The brief explanation of SOS (which starts at the top of the blog post) uses a toy dataset. This toy dataset has 6 data points. Each data point has two features. In other words, we have 6 data points in a 2-dimensional space. As for the roll call voting data, the dataset has 103 data points, where each data point has 172 features. The outlier probability of a senator depends on the location of its corresponding data point in the 172-dimensional space.