This is how I use my lap times. I care most about the efficiency and St. Deviation. Efficiency is just fast lap divided by my avg lap. As stated above, if there's a large gap then you are inconsistent in your driving. St. Deviation is just another way of telling you how tight your times are, smaller the number the better. Total laps is just running total of my practice laps during a season. Good way to keep track of maintenance, as I write short notes after each session.