Question about stochastic oscillator source code

[Overweight]

In stochastic oscillator code at (\MQL4\Indicators\Stochastic.mq4) on line number = 90,117,141 this code exists:

pos=prev_calculated-2;

My question : similar to other indicator, why is not this?

pos=prev_calculated-1;

I chose the second method, but there was no change in the results !?