The issue is in the dropdown menu first found while creating a new agent. However, this issue is not limited to agent creation. I recreated the issue in the Manage Jenkins → System.

This issue is not happening on all the Dropdowns; on the System screen, I see a few dropdowns showing the option correctly, and some dropdowns showing the option incorrectly. Based on the resolution of the screen.
 

Steps to Reproduce

 
Browser Tested:

• Chrome Issue exist

• Edge Issue exist

• Safari Working fine

• Firefox Working fine

To reproduce the issue, you must use Chrome as a browser(possibly a chromium issue) and use the Zoom level at 100%. This is happening for Mac. 

New Node

• Go to Manage Jenkins -> Nodes -> New Node.

• Assign a new name and Permanent Agent

• You can try to choose in any of the dropdown menus like Usage , Launch method or Availability and you will see the described behavior. 

System Config

• Go to Manage Jenkins -> System

• Usage : Not rendering correctly

• Global Trusted Pipeline Libraries → Select Source Code Management as GitHub

• • Discover branches --> Strategy : Not rendering correctly

• • Discover pull requests from Origin: Rendered correctly for me based on the resoltion

• • Discover pull requests from Fork: Rendered correctly for me based on the resolution

• • Trust : Not rendering correctly