The lead is the length of line in feet that your linecounter reads from the lure to your inline board.If running a dipsey have the rod in a horizontal position in rodholder.The rod tip is usually a couple feet above the water,but the lead is still from the dipsey to rod tip,or what your line counter is reading in the rod holder.If flatlining,with rod sitting in rod holder in back of boat in vertical position,the depth of rig you are running can be difficult to figure,due to rod tip being so high above the water.You have to remember,that the dive charts are a guide to get you close to depth you want your lure to run.It is very difficult to know precisely how deep all your gear is running.There are to many variables that can affect how deep you really are fishing.Your goal when you begin each day is to figure out what depth active fish are feeding,and what type of lure or bait they want to eat.The best way to figure out the depth,is to cover the water column with the lines you have out.Say,you are fishing in 30 feet of water(FOW).The fish on bottom are usually not active fish,but the may still bite.You also know they may come up 4-10ft to hit a lure.I would set my 4 lines to cover 10,16,20and 24 ft down.That should cover a good part of the water.After you catch several fish,you can figure out what lead(depth) the fish are biting and can switch other lines to match what is catching.