Well here's the example. I have SP Green Vegeta with 822.466 Total HP and I bring EX Raditz that boost 17% HP.
If I calculate (822.466*17%)+822.466 = 962.285. But in the picture my Vegeta have 932.602 HP, that means this is the wrong calculation. Then the calculation must be.
Base HP = Total HP - Soul Boost HP
= 822.466-174.608
= 647.858
Actual Battle HP = (Base Hp * Z Ability or Equipment) + Total HP
= (647.858*17%)+822.466
= 932.602
That's how the calculation works.
So the conclusion is Total HP isn't same as Base HP. And Total HP is Base HP + Soul Boost HP.