I am developing a solution, which calculates 10 min time-weighted average in real time (whenever the 10 min period is closed). I am using AF SDK for this purpose. The program is listening for new events in archive pipe and when the 10 min period is closed then it calculates the average using PIPoint.Summaries. Using this approach was fine until I subscribed to more points and then I have experienced performance issues with PIPoint.Summaries method. Because of this I wanted to try to implement this calculation by myself in C# code. I have found the article in Osisoft Live Library (PI Server) describing this calculation, but after implementing it, my results differ from what is returned by Summaries method. I wanted to study this topic more in order to find out what might be wrong with my implementation, but the only additional information I have found (pointed in Live Library article) is knowledge base article KB01585 (OSIsoft Customer Portal), which is no longer available. Do you know any articles, which I can study in order to get more detailed knowledge on this topic?