Some lumber is visually graded and some is mechanically graded. From the designations I suspect that the DSS designation is a visual designation and T2400 is a mechanical designation. In either case an allowable stress can be determined which needs to be compatible with the design of the truss. There may or may not be a problem but in any case you should resolve the issue.
The detailed design of these trusses is delegated to the manufacturer of the trusses who has an engineer who performs the calculations and seals and signs the design. From a code perspective the truss design is treated as a delegated submittal which should have been submitted to the building department.
The way to resolve this question is to have the engineer who designed the truss address the possible discrepancy.
How to resolve this issue is complicated by not knowing your role in this project, whether there was an architect of engineer involved in preparing the construction documents. Typically the architect or engineer who designed he project would be the one to respond to this question. They should know who to ask.
If there is no architect or engineer involved in the design of the project you might be able to request the contractor who subcontracted the design and fabrication of the trusses to refer this question to the engineer who designed the trusses.
You could report this to the building department but I would do this only if I could not get a response from the engineer who designed the trusses.
If this approach does not work you are obviously dealing with a dysfunctional system. In which case you may need to hire a local engineer to help you resolve this apparent discrepancy.
