Power Query Merge - populate only first match

Hi agajka ,
You can try the following code

let
    Source1 = #"Table 1",
    Source2 = #"Table 2",
    GroupedTable = Table.Group(Source1, {"Opportunity"}, {{"AllData", each _, type table [Opportunity=nullable text, IPA=nullable text]}}),
    AddIndex = Table.TransformColumns(GroupedTable, {"AllData", each Table.AddIndexColumn(_, "Index", 1, 1, Int64.Type)}),
    #"Expanded AllData" = Table.ExpandTableColumn(AddIndex, "AllData", {"Index"}, {"Index"}),
    MergedTables = Table.NestedJoin(#"Expanded AllData", {"Opportunity"}, Source2, {"Opportunity"}, "Table2", JoinKind.LeftOuter),
    #"Expanded Table2" = Table.ExpandTableColumn(MergedTables, "Table2", {"Number"}, {"Table2.Number"}),
    AddCustom = Table.AddColumn(#"Expanded Table2", "Number", each if [Index] = 1 then [Table2.Number] else null),
    #"Removed Columns" = Table.RemoveColumns(AddCustom,{"Index", "Table2.Number"})
in
    #"Removed Columns"

Final output

Best regards,
Albert He

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