Originally Posted by
mustang7757 Welcome to AC!
If your OS system is changing it could be from a update that adds or sometimes lower system that's just what resources it takes to run the device. Apps are different thing if you can show screenshot what you mean is changing app size or cache size like in my screenshot, you can go to individual apps by long press it then tap info>storage

Thank you for answering my post.
Here is a screenshot of my Storage. You can see the section System. After internet browsing it is now increased from 17,80 GB to 17,86 GB. When I clear the Chrome cache, Android OS size will go back to 17,80 GB. There are no installed updates to Android OS. Probably I have nothing to worry about since there is 128 GB of storage and the OS won't go wild in size :)