Since I know Tweakle has a good dead, I'll add that those pulling over double bodyweight for the duration of the program generally scale down that lift to 3x3 for the duration. Stronger lifters might also break out the Wed workout into 2 sessions or separate days if it gets too taxing.
The whole idea behind loading/deloading is that the initial volume is meant to be too much. It can't be sustained for more than a fixed number of weeks before dropping someone into overtaining. You scale right to the point of overreaching and then deload. The body can handle a lot more load over a short period than it can over an infinite one so this manipulation of accrued fatigue results in delayed compensation/adaptation - a rebound like effect which shows up in the deload period. This is a quick and dirty explanation: http://forum.mesomorphosis.com/showpost.php?p=48&postcount=3
The whole idea behind loading/deloading is that the initial volume is meant to be too much. It can't be sustained for more than a fixed number of weeks before dropping someone into overtaining. You scale right to the point of overreaching and then deload. The body can handle a lot more load over a short period than it can over an infinite one so this manipulation of accrued fatigue results in delayed compensation/adaptation - a rebound like effect which shows up in the deload period. This is a quick and dirty explanation: http://forum.mesomorphosis.com/showpost.php?p=48&postcount=3