Convert data range to a mappable list

Here's a (somewhat pedestrian)  way of doing that in Power Query. I am sure there are more elegant solutions.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCk7MSS1W0lEytDJWitWJVnLOLy4Bck3AnJDECiDb1MpMKTYWAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Transaction Type" = _t, Range = _t]),
    #"Added Custom" = Table.AddColumn(Source, "Custom", each let 
     d= Text.PositionOf([Range],":"),
     r= if d = -1 then List.Numbers(Number.FromText([Range]),1) 
                else List.Numbers(Number.FromText(Text.Start([Range],d)),1+Number.FromText(Text.End([Range],Text.Length([Range])-d-1))-Number.FromText(Text.Start([Range],d)))
   in 
      r
),
    #"Expanded Custom" = Table.ExpandListColumn(#"Added Custom", "Custom")
in
    #"Expanded Custom"

Anonymous it is pretty straight forward, start new blank query and click advanced editor and paste the following code

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WCk7MSS1W0lEytDJWitWJVnLOLy4Bck3AnJDECiDb1MpMKTYWAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [A = _t, B = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"A", type text}, {"B", type text}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Pos", each Text.PositionOf([B],":")),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "List", each if [Pos]=-1 then {Number.FromText([B])} else 
{Number.FromText(Text.Middle([B],0,[Pos]))..Number.FromText(Text.Middle([B],[Pos]+1))}),
    #"Expanded List" = Table.ExpandListColumn(#"Added Custom1", "List"),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded List",{"Pos"})
in
    #"Removed Columns"

. The main logic is in step #"Added Custom1"