Need urgent help - DAX calculation

Hi Kolumam ,

as the others have mentioned already, the problem with the sample you've provided is that there are inconsistencies/errors in it that make determine the desired logic hard.

The following code calculates proportional values according to the actual number of days in the year: 

let
    Source = Table.FromRows(
        Json.Document(
            Binary.Decompress(
                Binary.FromText(
                    "dc1LCsAwCATQu7gOqPkQc5OW4P2vUQ2RhkJ3M/IY5wTGjpl4QILCKJEv772BJifjIMVypk0qbZKxxd2MVSscOxI71Xf6u8Ni+V6ETiKfV04qb8I/r9YOFVB9AA==", 
                    BinaryEncoding.Base64
                ), 
                Compression.Deflate
            )
        ), 
        let
            _t = ((type nullable text) meta [Serialized.Text = true])
        in
            type table[
                #"Start Date of Contract" = _t, 
                #"End Date of Contract" = _t, 
                #"Operation Name" = _t, 
                #"Comprehensive O&M Price" = _t
            ]
    ),
    #"Changed Type" = Table.TransformColumnTypes(
        Source, 
        {
            {"Start Date of Contract", type date}, 
            {"End Date of Contract", type date}, 
            {"Operation Name", type text}, 
            {"Comprehensive O&M Price", Int64.Type}
        }
    ),
    AddListOfYears = Table.AddColumn(
        #"Changed Type", 
        "Year", 
        each {Date.Year([Start Date of Contract])..Date.Year([End Date of Contract])}
    ),
    #"Expanded ListOfYears" = Table.ExpandListColumn(AddListOfYears, "Year"),
    AddStart = Table.AddColumn(
        #"Expanded ListOfYears", 
        "Start", 
        each List.Max({[Start Date of Contract], #date([Year], 1, 1)})
    ),
    AddEnd = Table.AddColumn(
        AddStart, 
        "End", 
        each List.Min({[End Date of Contract], #date([Year], 12, 31)})
    ),
    AddDuration = Table.AddColumn(
        AddEnd, 
        "DurationInDays", 
        each Duration.Days([End] - [Start]) + 1, 
        Int64.Type
    ),
    AddDaysInYear = Table.AddColumn(
        AddDuration, 
        "DaysInYear", 
        each if Date.IsLeapYear(#date([Year], 1, 1)) then 366 else 365
    ),
    AddAnnualShare = Table.AddColumn(
        AddDaysInYear, 
        "AnnualShare", 
        each [DurationInDays] / [DaysInYear]
    ),
    WeightPriceByShare = Table.AddColumn(
        AddAnnualShare, 
        "AnnualContractValue", 
        each [#"Comprehensive O&M Price"] * [AnnualShare], 
        type number
    )
in
    WeightPriceByShare

It creates a table in the query editor that will hopefully allow you to follow the logic and see where your numbers are wrong:

In general your numbers are too low because your using 365 days a year and weight your months only with 30 days (adding up to 360).

A specific inconsistency in your calculation is that you allocate partial end years pro rata (i.e. Y 410 for 2020: 90 days (Jan-Mar)) but all partial start years with full year (Y 380 with 365 days, although the contract starts in April and X 395 divided by only 180 (instead of 360)). 
So my calculation assumes that the "Comprehensive O&M Price" is an annual fee that has to be allocated to partial years consistently.