In the (x) spot, you can put S,M,L,H,F,W,P....or small, medium, large, hoppers, fuzzy, weaner, pinkie...or whatever you classify your feeder size as, or you can put down the number of the type of prey you fed. The @ is just a quick way to make it say rAT, as @=at. I guess the ASF spot deserves an (x) as well, but I Greg was the one that added it to the key and I dont specify the size of ASFs personally.