Modify indentation between label and content in LyX

I have the following list, created with the ‘Labeling’ list style in LyX:

LyX seems to automatically add a large indentation (e.g. between ‘AB1’ and ‘Test’) whenever pressing space or tab past the label.

LyX exports the following LaTeX code:

%% LyX 2.3.5-1 created this file.  For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
documentclass[oneside,english]{amsart}
usepackage[T1]{fontenc}
usepackage[latin9]{inputenc}
usepackage[a4paper]{geometry}

usepackage{amsthm}

makeatletter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands.
numberwithin{equation}{section}
numberwithin{figure}{section}
newenvironment{lyxlist}[1]
    {begin{list}{}
        {settowidth{labelwidth}{#1}
         setlength{leftmargin}{labelwidth}
         addtolength{leftmargin}{labelsep}
         renewcommand{makelabel}[1]{##1hfil}}}
    {end{list}}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% User specified LaTeX commands.
usepackage[T1]{fontenc}
usepackage{lmodern}

makeatother

usepackage{babel}
begin{document}
begin{lyxlist}{00.00.0000}
item [{AB1.}] Test
begin{lyxlist}{00.00.0000}
item [{a)}] Test
end{lyxlist}
item [{AC2.}] Test
end{lyxlist}

end{document}

How can I reduce the length of this indentation?