The Mages and the Masons have a total of 4 people. The Townsfolk have 7.
The Mages and the Masons have a total of 4 Mechanoids. The Townsfolk have 4.
Secondly, you can see that these are weak probabilities. If the check results in a Mechanoid, then nothing can be said at all. If it's a person, then with a higher probability, they are Town. But we are more interested in belonging to the Mafia :)