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NAS-5GS wrong length definitons?

Hi,

I find some definitions in NAS-5GS protol strange - such as:

NAS protocol spec (3GPP TS 24.501 V15.1.0 (2018-09)) defines the lengths of some parameters as follows:

AMF Region ID = 8 bits

AMF Set ID = 10 bits

AMF Pointer = 6 bits

However Wireshark code defines these as follows in "epan\dissectors\packet-nas_5gs.c":

    { &hf_nas_5gs_amf_region_id,
    { "AMF Region ID",   "nas_5gs.amf_region_id",
        FT_UINT16, BASE_DEC, NULL, 0x0,
        NULL, HFILL }
    },
    { &hf_nas_5gs_amf_set_id,
    { "AMF Set ID",   "nas_5gs.amf_set_id",
        FT_UINT8, BASE_DEC, NULL, 0xf0,
        NULL, HFILL }
    },
    { &hf_nas_5gs_amf_pointer,
    { "AMF Pointer",   "nas_5gs.amf_pointer",
        FT_UINT8, BASE_DEC, NULL, 0x0f,
        NULL, HFILL }

So,

AMF Region ID is defined as 16 bits as opposed to 8 bits definition in the spec.

AMF Set ID is defined as 8 bits as opposed to 10 bits definition in the spec.

AMF Pointer is defined as 8 bits as opposed to 6 bits definition in the spec.

And furthermore, when I analyze these parameters in NAS-5GS messages, Wireshark decodes them as in following lengths:

AMF Region ID - 16 bits

AMF Set ID - 4 bits

AMF Pointer - 4 bits

Why is this discrepancy? Anybody else has seen this?

PS. I am using today's latest "wireshark-2.9.0rc0-2526-g9ea94e29.tar"