most data books listings are on the low side or in this case the short side.if your a little over the max length its not going to hurt anything.they do this becouse the longer the case the closer the bullet is to the lands and groves,the closer the bullet the higher the pressure.unless you can monitor pressure increases and other high tech aspects of reloading its a good idea to stay within the limmits of the guide books.the most important thing is to pick a length(within the limmits) and keep all your cases at that length.