You don't adjust anything. It raises the pressure to 4. Mine broke after 10 years of use at home, winter and summer. I ordered the same one. Most likely, for this price, it will either break in 1-2 years or it will last a decade and be forgotten by God and still work.

I bought the ingko one which is exactly the same as the total one. You can't adjust anything, it just goes to 1.5 bar and cuts off at 10+ the input pressure, which means at 12. Useless and dangerous.