Hi guys. Im having trouble with my petroleum engineering course. I have attached the example thats giving me problems, start at 1.1.1 limits and just read through to the second pic where it states that the graph at 3 sec shows a height of -96.522ft and at 2 and 4 secs the height is at -48.261ft and -241.305. Am I missing something here? I have no clue where these numbers came from. Theres a formula on pic 1 but I can't seem to get the same answers and also from the graph the heights are not coinciding with time. This is a renowned handbook that pro's use so it's not a mistake. Any help appreciated!