It is an application that helps you calculate some of the variables like event duration , interval , clip length and the number of photos when you are shooting a timelapse using the intervalometer. You must know few variables before hand to calculate what you want to calculate. For example you should know that you want to make a timelapse that will be 10 seconds long @30fps and the interval that you are putting is 5 seconds. Maybe then you want to calculate if i want a timelapse like that how many photos i should set and for how long will the process of the camera shooting those number of photos take?(Event duration).