the estimated mash efficiency is not editable..it is a calculation by the program itself based off measurements you can take and plug in during brew day (such as pre-boil gravity, post-boil gravity, etc), and based off the numbers given it gives the estimation of what your efficiency should be. you can change your efficiency itself (measured, or what you know your system's efficiency is) by clicking on your recipe as if you were editing the recipe (adding/removing ingredients screen) and simply clicking on the number in the "Tot efficiency" field up top..