Power Query Syntax

List.Min({[Calendar.Year]}) just returns the minimum Calendar.Year of each rows Calendar.Year, in other words: just the value of each rows Calendar.Year value.

Instead, you must use the minimum value of the entire table column.

Example query:

let
    Source = #table(type table[Calendar.Year = Int64.Type],List.Zip({{1985..2020}})),
    MinYear = List.Min(Source[Calendar.Year]),
    #"Added Custom" = Table.AddColumn(Source, "WrongCode", each [Calendar.Year] - List.Min({[Calendar.Year]})),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "CorrectCode", each [Calendar.Year] - MinYear)
in
    #"Added Custom1"