Convert the column into duration - Throwing an error

bourne2000  Try something like this (paste into new blank Query in advanced editor)

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMrS0MrIAIqVYHSDH2MrA0MrEAMwxMrEytLAyNlGKjQUA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Talk Time" = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Talk Time", type text}}),
#"Split Column by Delimiter" = Table.SplitColumn(#"Changed Type", "Talk Time", Splitter.SplitTextByDelimiter(":", QuoteStyle.Csv), {"Talk Time.1", "Talk Time.2", "Talk Time.3"}),
#"Changed Type1" = Table.TransformColumnTypes(#"Split Column by Delimiter",{{"Talk Time.1", Int64.Type}, {"Talk Time.2", Int64.Type}, {"Talk Time.3", Int64.Type}}),
#"Inserted Integer-Division" = Table.AddColumn(#"Changed Type1", "Integer-Division", each Number.IntegerDivide([Talk Time.1], 24), Int64.Type),
#"Inserted Modulo" = Table.AddColumn(#"Inserted Integer-Division", "Modulo", each Number.Mod([Talk Time.1], 24), type number),
#"Merged Columns" = Table.CombineColumns(Table.TransformColumnTypes(#"Inserted Modulo", {{"Integer-Division", type text}, {"Modulo", type text}}, "en-NZ"),{"Integer-Division", "Modulo"},Combiner.CombineTextByDelimiter(".", QuoteStyle.None),"Merged"),
#"Merged Columns1" = Table.CombineColumns(Table.TransformColumnTypes(#"Merged Columns", {{"Talk Time.2", type text}, {"Talk Time.3", type text}}, "en-NZ"),{"Merged", "Talk Time.2", "Talk Time.3"},Combiner.CombineTextByDelimiter(":", QuoteStyle.None),"Merged.1"),
#"Changed Type2" = Table.TransformColumnTypes(#"Merged Columns1",{{"Merged.1", type duration}})
in
#"Changed Type2"