Not necessary DT1 must include you to become DT2, numbers of DT2 can include you to become a DT2 also.
This is wrong.
For being a DT2 member, you need to be in trust list of at least 1 DT1 member and the number of DT1 members who have included you from their trust list must be bigger or equal to number of users who have excluded you from their trust list.