Variable Load Strategies

I understood the principle of this strategy

"Interval to the desired value and the Variance to the how much the number of threads should decrease and increase"

But how this behaves when the response time becomes bigger then the variance interval ?

So i have 10 threads still running and it should now go to execute 5 threads then to 15 etc ? What will happen ?

cause the 10 threads are still ongoing...having some slow responses