ᐅ Is it possible to adjust the water volume of the small flush on a toilet?

Hello,
We have a toilet system from the company "Jomo" installed.
As you can see in the picture, it has standard flush buttons—a large and a small one. However, both buttons release the same amount of water. How can I adjust the small button so that it uses an appropriate amount of water for a "small flush"? I have already removed the cover and the components behind it (just enough to access the internal mechanism). I turned the fill valve many times to the left, but the same volume of water fills the tank regardless. How can I adjust the small flush?

Best regards,
Alex

As a rule, the corresponding instructions can be found on the internet.

There is a QR code that you can scan for the supposed instructions and spare parts, but then I end up on the company’s website that installed it, and there are no instructions at all.

Take off the cover and take a picture. Maybe then someone can identify what type of flush tank it is.
How did you determine that the same amount of water always flows?

I just searched for Jomo on Google. The first result was the manufacturer. There was also a link to the user manual right there.

I can tell simply by seeing (and hearing) that the same amount of water is flowing... and also from their website... of course, I have looked at the installation manual, but that doesn’t help me much since it’s "just" the installation manual.