Is it possible to adjust the water amount for the small toilet flush?

Hello,
We have a toilet system from the company "Jomo" here.
As you can see in the picture, it has normal flush buttons, one large and one small .. Both buttons, however, release the same amount of water; how do I adjust the small button so that the amount of water is sufficient for the "small business"? I have already removed the lid, as well as the parts behind it (only enough to access the "inner workings") .. I have turned the fill valve many times to the left, but the same amount of water still goes into the water tank. How do I adjust the small flush?

Best regards
Alex

As a rule, the corresponding instructions are available on the Internet.

There is a QR code that you can scan for the supposed manual and spare parts .. but then I arrive on the homepage of the company that installed it and there is nothing like a manual ..

Take off the cover and take a picture. Maybe then someone will recognize what kind of cistern it is. How did you determine that the same amount of water always flows. I just typed Jomo into Google. The first result was the manufacturer. And there was a link to the instruction manual right there.

I simply notice this by seeing (and hearing) that the same amount of water flows there... and that on their homepage... of course I saw the installation instructions there, but that doesn't help me because it is "only" the installation instructions.