B5 and margintoc

[Neogene]

Hi,

I'm using the following document class which uses B5 document paper format, twosided:

\documentclass[
b5paper,
fontsize=10pt, % Base font size
twoside=true, % Use different layouts for even and odd pages (in particular, if twoside=true, the margin column will be always on the outside)
%open=any, % If twoside=true, uncomment this to force new chapters to start on any page, not only on right (odd) pages
%chapterprefix=true, % Uncomment to use the word "Chapter" before chapter numbers everywhere they appear
%chapterentrydots=true, % Uncomment to output dots from the chapter name to the page number in the table of contents
numbers=noenddot, % Comment to output dots after chapter numbers; the most common values for this option are: enddot, noenddot and auto (see the KOMAScript documentation for an in-depth explanation)
%draft=true, % If uncommented, rulers will be added in the header and footer
%overfullrule=true, % If uncommented, overly long lines will be marked by a black box; useful for correcting spacing problems
]{kaobook}

And a chapter which starts with:

\setchapterstyle{kao}
\setchapterpreamble[u]{\margintoc}
\chapter{Fondamenti di matematica e fisica}
\labch{math}

\section{Materie tanto interessanti quanto poco apprezzate}
\labsec{mathintro}

...

The problem is that margintoc displayed on the right showing chapters/subchapters titles exceed the page margin, how can I reduce the left margin/padding of this content area?