I need help understanding this dax code and the functions used in it. Calculate, filter.

Anonymous It is doing something because of how CALCULATE replaces filtering context and the fact that you are operating essentially in the context of ALL when you are doing those CALCULATE statements. The variables at the beginning are just preserving the row context that you want to use later. You can think of the first CALCULATE statement like the following:

SUMX(
  FILTER(
    ALL('Source_With_Trace_ID'),
    [Item_Number] = _item_number
    && [Casting_Date] >= _start_date
    && [Casting_Date] < _cast_date
  ),
  [Inclusion]
)