The true meaning of spliting torque

I've read all I can find on the different approaches to allocating power to the Forester's wheels depending on MT or AT. But I've not read an explanation of a simple question: what exactly does it mean that, say, 60% of torque is going to the front wheels and 40% to the rear? Further, how is that metered? (Yes, of course, the computer does it, but what's the instrumentation?) And if somehow I could measure the torque in a situation where my XT is running at exactly 3,600 RPM, and there was a 60/40 split in effect, exactly 60% x 235 ft lbs (max rating on the XT turbo engine) or 141 ft lbs would be going to the front wheels and, therefore, 94 ft lbs would be going to the rears? Given the limited-slip dif in the rear, could, say,

20% of that (18.8 ft lbs) go to one wheel and 75.2 ft lbs to the other? Is the need for torque presumably gauged by the number of wheel revolutions in a given time period relative to the other wheels, the other wheel on the same "axel" considered first, then those at the other end of the car? OK, enough questions.