Why garbage can appear again in a few seconds after cleaning?
Because your Windows OS is still working. It's normal. Every second some background process can create log file or temporary file, and regular computer has over 50 services running in the background. Every launched application (for example, if you just restart our app) will create at least prefetch file and a record in the registry. All these are temporary garbage, but this is how Windows OS works.
Thus, right after you've done with cleaning, it is normal if some new garbage will be created within next few seconds and our application will show that. This is how computer works.
It's almost impossible to have completely clean computer for a long time. And the more apps you have - more garbage they will create. In our opinion, we recommend to ignore total amount of garbage less than 5-10 megabytes. Anyway, everywhere, some garbage will be created, just keep it in a acceptable size.