Pie chart bug?

Greetings,

I found out that you can press the Function Three and Shift key and a pie chart will appear in the bottom right corner of the screen. The pie chart acts normal until I switched item slots. When I switched item slots, the entire pie chart switched to a green color meaning unspecified. This pie chart remains until I close and reopen the game. I am unsure if this is a bug or if this is normal but I thought I might as well check to be sure.

Steps to duplicate:

Open your minecraft game.

When you're in a single player or multiplayer world (it works in both), press the function three and shift keys, a pie chart should appear in the bottom right corner.

Switch item slots and the pie chart should turn green entirely meaning unspecified.

The pie chart will remain that way until the game is closed and reopened.

If you have any questions or comments, contact me via the comment section.

Thank you for you're time on resolving this matter.

-Legonxtcreator