If you follow the link in my signature on how a wdh works, that may give a little more info and make it easier to understand.
To sum it up:
TV only: say the fa (front axle) weighs 3000lbs
TV w/ tt hooked up, but without the wd bars latched up: say the fa weighs 2600lbs. So you "lost 400lbs" by hooking the tt up without the wd bars.
TV w/ trailer hooked up and th wd bars latched up: you want the hitch head tilted so that you transfer enough weight back to the fa per you tv owners manual. If it states to restore 100% of the "lost weight", then you want to adjust the wdh head so when the bars are hooked up, the fa weighs 3000lbs again. If it is 50%, then the fa should weigh 2800lbs, 25%- 2700lbs.
When you hook up a trailer and use a wdh, there is some weight that is "transferred" to the tt axles, but the amount is not very much, and it is generally suggested to count the total tw toward the tv payload. The other thing to keep in mind is the tv receiver hitch rating.
I need to weigh our rig again as some things have changed, but here is from the first time I weighed the combo.
Left weights- truck and trailer w/ wd bars hooked up
Middle weights- truck and trailer w/ wd bars unhooked
Right weights- truck only
Top to bottom weights are:
You can see that I have restored 100% of the lost weight from the fa. While transferring 540lbs back to the fa, I only transferred 240lbs to the ta. Which with a 1400lb tw, that is not very much weight transferred to the ta.
Hope this helps!!!