As I have related many times in the past, I learned to dive using tables 20 years ago. On my first dive trip (Cozumel), I tried to use my tables after my first DM-led multi-level dive, and I found I was off the tables by a long shot. I got a computer before my next trip. My attempt to use tables on that dive remains the only time I have ever seen any recreational diver attempt to use tables (or eRDPml, which is the same thing) for dive planning outside of a class.When I was first learning how to operate it I was having the same problem and then I read the manual http://elearning.padi.com/company0/tools/eRDPML_InsforUse.pdf and watched some youtube videos. It was not very intuitive to me for some reason. I would also contend that if everyone had to learn the tables initially then LDS would sell a lot more computers.