DAX vs Sum calculation (Difference in total)

[NielsT]

At the day level are the results of the two formulas the same, only at the week level they are different (Difference in total = 5391.02 - 5378.52 = 12.5).
Can someone explain this or what am I doing wrong?

Each day is one line per employee in the data set.

Formules

Aantal_FTE  =

Sum(Fact_Medewerker_Verzuim[Aantal_FTE]),

# FTE in dienst (1) = 

VAR MaxSelectionDate = MAX ('DIM_Kalender'[Date] )

VAR MinSelectionDate = MIN ('DIM_Kalender'[Date] )

RETURN

    CALCULATE (

        Sum(Fact_Medewerker_Verzuim[Aantal_FTE]),

        FILTER (

            'Fact_Medewerker_Verzuim',

            ( Fact_Medewerker_Verzuim[Datum_In_Dienst] <= MinSelectionDate && Fact_Medewerker_Verzuim[Datum_Uit_Dienst] >= MaxSelectionDate )          

        )

    )

Thanks in advance for your help!

[Greg_Deckler · Accepted solution]

@NielsT This looks like a measure totals problem. Very common. See my post about it here: https://community.powerbi.com/t5/DAX-Commands-and-Tips/Dealing-with-Measure-Totals/td-p/63376

Also, this Quick Measure, Measure Totals, The Final Word should get you what you need:
https://community.powerbi.com/t5/Quick-Measures-Gallery/Measure-Totals-The-Final-Word/m-p/547907