To be honest, i'm also not sure what exactly mean:
"The second number is the number of reported scams." - the one thing connected with this formula is report of forum rules violation.. This is it?
No. The trust score has nothing to do with reporting things to moderators. This number is the number of negative feedbacks given to this person by the people in your trust list.
an the third number:
"The third number increases with the number of positive reports" - who gives positive reports? As i can understand, when someone from DT members give positive report, this is changing "first number". So what reports change third number?
This is the number of positive feedbacks given by people in your trust list.
The trust that you see is entirely based upon who is in your trust list. If you did not change the trust list, then you are using DefaultTrust.