[Manyula]

For now, the progress is calculated in percent, so 0.0 is the minimum and 100.0 is the maximum value.
So, if 20 seconds are 100%, then 1 seconds equals 100/20 = 5%. So, each second, you would have to increase the value by 5.0.

I realize, this might be a bit inconvenient to use. I might add "min_value" and "max_value" parameters and let the function do the calculations for you in the near future.