anchor.diff:  encode_extensions([#client_hello_versions{versions = Versions0} | Rest], Acc) ->
       Versions = encode_versions(Versions0),
       VerLen = byte_size(Versions),
  -    Len = VerLen + 2,
  +    Len = VerLen + 1,
       encode_extensions(Rest, <<?UINT16(?SUPPORTED_VERSIONS_EXT),
  -                              ?UINT16(Len), ?UINT16(VerLen), Versions/binary, Acc/binary>>);
  +                              ?UINT16(Len), ?BYTE(VerLen), Versions/binary, Acc/binary>>);
   encode_extensions([#server_hello_selected_version{selected_version = Version0} | Rest], Acc) ->
       Version = encode_versions([Version0]),
       Len = byte_size(Version), %% 2
  
positive.code: 
  decode_extensions(<<?UINT16(?SUPPORTED_VERSIONS_EXT), ?UINT16(Len),
                         ExtData:Len/binary, Rest/binary>>, Version, MessageType, Acc) when Len > 2 ->
      <<?UINT16(_),Versions/binary>> = ExtData,
      decode_extensions(Rest, Version, MessageType,
                        Acc#{client_hello_versions =>
                                 #client_hello_versions{
  
negative.code: process_supported_versions_extension(<<?UINT16(?SUPPORTED_VERSIONS_EXT), ?UINT16(Len),
                                         ExtData:Len/binary, _Rest/binary>>,
                                       LocalVersion, _LegacyVersion) when Len > 2 ->
      <<?BYTE(_),Versions0/binary>> = ExtData,
      [Highest|_] = decode_versions(Versions0),
      if Highest =< LocalVersion ->
              Highest;
  