When the above simulation in default state: (not in [b][b]dial[/b][/b] mode).
The lower half is shown in [b]mm[/b], and the upper half is shown in [b][b]inch[/b][/b].

When the [b]dial[/b] mode check-box is checked:
The value will be shown in inch when [b]inch [/b]check-box is checked.