The slider for render distance in the configuration screen does not always indicate the current distance actually being used.

Steps to reproduce:

1. Open the Game Menu.
2. Tap the "Options" button.
3. Select the "Graphics" tab.
4. Set the Render Distance to the maximum.
5. Close the menu to return to the game.
6. Repeat the steps above from the beginning until you see the slider for the Render Distance moved to the minimum or the middle on its own, while the number of chunks actually rendered stays the same.

This might have something to do with the amount of free RAM currently available but I'm not sure.