EDIT: This is total conjecture.
only 1 or at most a few of those 21 features represent real data. The real data represents similar information to the insider information which they wish to act upon.
Example data prep:
1. Insider source says that a contract is falling through, a patent is being filed for, quarterly numbers have been missed/surpassed etc.
2. Similar information is gathered from historic performance data of the company, similar companies or market segments.
3. The information is correlated with whatever metric they wish to move along and encoded in one of the 21 feature classes.
4. Repeat for whatever relevant information that can be linked to the insider source - i.e. competing companies, re-encoding separately for long and short positions etc.
5. Fill in remainder of 21 feature classes with noise.
6. Profit.