The T mark will line up both at TDC on compression and exhaust stroke though. I found the easiest way on the 450 is to just do each valve seperately, turn the crank until the cam lobe points straight up, and then adjust. There are other marks on the camshaft you can look at to see if its at TDC on compression but on my bike they werent there (should be an index mark on the cam that lines up with a score mark on the head, the mark on my cam didnt exist).
Also remember on the adjusters, the index mark needs to face OUT from the motor. If you turn it far enough around that the index mark points towards the center of the engine, you can get the clearance right but the cams wont open the valves properly.
I also like to set my clearance to 0.04mm which is 0.0015" (0.03mm is the honda recommended clearance).