Zero, Nothing, Zilch, Nada.
Well it is slightly more than that, Like I know it is an approximation of the value a players has to their team. The value is a way of rating all players by one number regardless of position. The number also approximates that value in wins that player has over a replacement player (AAA/AAAA player)
A team full of replacement players would win an estimated 50 games, which means some recent Astros teams were basically replacement teams.
WAR is comparable between eras. and 8.0 WAR today is meant to be an apple to apple comparison to the WAR of previous eras. WAR can be used to compare Babe Ruth, Cy Young, Ted Williams to Clayton Kershaw, Cole Hamels, Mike Trout and Steve Jeltz or any other player past/present.
But beyond that info, I am not really sure how WAR is calculated. I trust Sean Forman, Baseball-ref, FanGraphs and Baseball Info Solutions have done their due diligence and stand by the product they have created.
I am presenting this purely as a reference to my own understanding of WAR and where I am coming from when referring to WAR and or making projections about WAR.