It sounds like your missing the point of TD. As written in the guide, TD is meant to correct for overboosting or underboosting after you have your WGDC dialed in correctly. So if you are tuning in the current weather conditions, you should be able to get your boost correct by adjusting the WGDC tables only and have TD set to 0. Adjust both WGDC tables. If your initial value is 30 and your max is 50 and you are overboosting, move them to 25 and 45. That leaves the gap between them for TD corrections when you start using them again.
If you tune your car now with your WGDCs dialed in and everything is working with the TD zeroed out, in July you won't be hitting your target boost because the atmosphere has changed and the air has become less dense. Then TD should step in and work to correct for the boost error. Otherwise you'd have to retune your boost every time the weather changes.
It sounds like you're expecting to see a direct correlation between 1 table and 1 effect when it doesn't work like that. It's a dynamic self correcting system and you need to understand it's individual parts as well as the whole to really know what to change. Otherwise you make a change, you don't see the effect you were expecting, and end up getting frustrated because there isn't a directly cause-effect relationship.