There are two leg dimensions. One side of the T-joint is welded with the largest single pass weld and the other side is welded using the smallest multiple pass weld.
If you are qualifying the fillet weld in accordance with clause 4 it means the WPS does not meet the requirements for prequalification. Not only do you have to qualify the fillet welds, but you have to establish the WPS used produces the mechanical properties required. In short, you have to qualify a WPS using a flat grooved plate assembly (or pipe) to perform the requisite volumetric NDT, the reduced section tensile tests, and the guided bend tests. Don't forget the visual requirements of clause 4.9.1 is required before any additional NDT or mechanical testing is performed.
Suggested:
Qualify the fillet weld samples first (the fillet welds do not have to be on a single assembly) to establish the welding parameters, i.e., voltage, amperage, travel speed, wire feed speed, etc. Once acceptable fillet weld samples are welded, use those parameters to weld the grooved test assembly.
Best regards - Al