Punkte in xsim addieren

\documentclass{scrartcl}

\usepackage[ngerman]{babel}

\usepackage[utf8]{inputenc}
\usepackage[most]{tcolorbox}
\usepackage{xsim}
\usepackage{amsmath}



\ExplSyntaxOn
\NewDocumentCommand \XSIMifinstrTF {mmmm}
{ \tl_if_in:onTF {#1} {#2} {#3} {#4} }
\ExplSyntaxOff
%Aufgabenumgebung
\DeclareExerciseEnvironmentTemplate{tcolorbox}
{%
\tcolorbox[standard jigsaw,
opacityback=0,
opacityframe=0,
coltitle=black,
breakable ,
drop shadow ,
beforeafter skip = .5\baselineskip ,
title = 
\textbf{\GetExerciseName~\GetExerciseProperty{counter}}%
\GetExercisePropertyT{subtitle}{ \textit{\PropertyValue}}%
\IfInsideSolutionF{%
\GetExercisePropertyT{points}
{%
    \XSIMifinstrTF{\PropertyValue}{+}
    {$\PropertyValue = {}$}{}%
    \points{\PropertyValue}%
}%

}%
]%
}
{\endtcolorbox}

\DeclareExerciseType{klausuraufgabe}{
exercise-env = aufgabe ,
solution-env = loesung ,
exercise-name = Aufgabe ,
solution-name = Loesung ,
exercise-template = tcolorbox ,
solution-template = tcolorbox
}

\begin{document}

\begin{aufgabe}[points=2+2+2]
 Diese Aufgabe soll drei Unteraufgaben haben, welche jeweils 2 Punkte bringen.
\end{aufgabe}

\end{document}