Need some advice on Timing belt tension, green or silver spring?

[blueapple]

I read on the toyota repair manual posted on this site about setting the timing belt tension.
It says use the green spring, rotate the crank-shaft 1 7/8 revolution, stop at 45 degree, then tighten the pulley bolt.

It also mensioned something about silver spring earlier, but didn't say anything about what is it for. It's got higher spring constant, but what is it for? new belt? used belt?

and, is the spring force alone really enough? I know my question sounds stupid...
Could anyone who's done the job give me a detailed and correct method of getting the right tension?

Thanks!

[88 LE]

The spring sets the tension. After the bolt for the tensioner is tightened, the spring does nothing.

As for the green or silver spring, I don't know and don't worry about it. I just install everything and torque the tensioner bolt to spec.