Geometric Dimensioning and Tolerancing symbols (True Position, Concentricity, Profile) do not stack linearly. A good calculator interprets how a True Position tolerance of (\Phi 0.1) translates into a horizontal or vertical displacement in the stack.
The Worst-Case method assumes that every single part in the assembly is manufactured at the extreme limit of its tolerance—either all at maximum material condition (MMC) or all at least material condition (LMC). tolerance stack up calculator