Besides what mentioned,We should know a bit about what you plan to do.You developed your program in the horizontal direction and reached the Block nesting depth of the CPU that is really far to reach in a normal case . That means, you wanted to get result from your algorithm in one cycle of CPU ! For such algorithms develop it vertically in just one FC or use loop function.Nesting depth is a term in this context used for priority clasess ,it is CPU specific and start with one OB(Nesting depth#1).You can check that in properties of each CPU (S7-400H, CPU 414H)