The strap is approx. 160cm long and designed to fit also tall people. So, for smaller people it will be too long, but can easily be shortened like this:

1. De-mount strap from the metal piece.
2. Punch a new 3.5mm hole using a simple spring belt punch.
3. Cut the overlaying strap with a sharp knife. Use some leather balm and rub the freshly cut strap end.
4. Mount the strap again onto the metal piece. If the hole is still too tight, punch again with 4mm.
5. Done. Enjoy.

If you do not have the tools at hand, every shoe repair service can do the job in a minute.