let
Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
#"Grouped Rows" = Table.Group(Source, {"Category Number"}, {{"Data", each _, type table [Category Number=number]}}),
#"Added Custom" = Table.AddColumn(#"Grouped Rows", "Custom", each Table.AddIndexColumn([Data],"Unique",1,1)),
#"Removed Columns" = Table.RemoveColumns(#"Added Custom",{"Data"}),
#"Expanded Custom" = Table.ExpandTableColumn(#"Removed Columns", "Custom", {"Unique"}, {"Unique"})
in
#"Expanded Custom"