That assumes that both numbers are for the same period and that each arrest correspond to 1 match, which most likely will not be be true. For example if system

That assumes that both numbers are for the same period and that each arrest correspond to 1 match, which most likely will not be be true. For example if system identified only subset of people, but when you make arrest you arrest all. That means that now you have more arrest attributed to system, than number of matches. Since article does not do any attempt to answer these discrepancies, there is high chance the devil is in the details of definitions of those numbers.