Hi Andrei,
Actually, we do not support the project from the archived courses anymore. I am vaguely remembering this project.
may be I need some sort of restrictions in my coding?
Yes, that sounds like a good idea. 
If I remember correctly, the problem was caused by the incrementation of min and max in the OnPressHigher and OnPressLower methods.
The best would be to log the values into your console with Debug.Log to see what’s going on at runtime. Once you figured that out, implementing a restriction (if necessary) is relatively simple. If you need a restriction but do not know if-statements yet, look for C# if-statements online, for example, on DotNetPerls.
Also please feel free to ask our helpful community of students over on our Discord chat server.
Good luck!
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