Are you looking for a way to have your numeric keypad keys always enter digits as in Mac OS or is it currently exhibiting this behavior and you would like to know how to disable it? Either way, the option is available in Linux Mint. This has been tested on Mint 18.3 and should work in other versions.
- Goto MENU -> Preferences -> Keyboard
- Click the "Layouts" tab button at the top of the Keyboard dialog box
- Click the "Options" button at the lower right of the Layouts tab in the Keyboard dialog box
- Locate "Miscellaneous compatibility options" and click to expand
- Look for "numeric keypad keys always enter digits (as in Mac OS)" and Enable/Disable to your preference
