During my experience in few company, I found a kind of table to draw our s-curve, you can choose a number of period and you have the forcast corresponding of this period, the periode can be (hour, day, week or month), for exemple :
Number of period 4 / period( 1) 13.20% / period( 2) 27.50% / period(3) 36.40% / period(4) 22.90%
With this value you can draw your s-curve, DO you have any information about it ? or the function that you can insert only the number of period and you have the percent that you mus achieve in each period ?