It’s not surprising that you do not know that DT3 exist, because majority of forum members usually limit their trust list depth view to DT1 and DT2. That’s why the trust ratings by DT1 and DT2 are more visible and powerful than DT3.

You can customize your trust settings to include DT3 by adjusting your Trust Depth to 4, although it is recommended that you use the default Trust Depth which is 2.