I've avoided the "Every X Seconds" command because if I remember right, using "DT" is more accurate or stable.
You don't need to avoid "Every X seconds". It's already framerate independent, because as the name suggests, it works in seconds, not frames.
If you want to make your own time counter based on dt, then just adding dt is all you need to do. I'm not sure what you're trying to achieve with the calculation round((dt+1)/2) - there's no need to change it, just add dt by itself, and that's essentially a time counter in seconds. But you may as well use 'Every X seconds' or the Timer behavior for convenience.