When setting the input field text value through script to a negative integer value whilst the input field is in integer content mode the value will be incorrect. E.G Setting it to "-12345" will produce the value "-"

Included is an Editor test that demonstrates this.
To Run add the file to a project in a directory called "Editor" then open the editor test runner "Window/Editor Test Runner" and run the test, it will go red. Setting the value through through the UI(not script) works as expected.