SmartThings routine dimmer option doesn't go below 10%

Many inexpensive zwave dimmers, including the GE, won’t reliably dim below 10%. (More expensive switches which use a different kind of engineering can). That said, smart bulbs certainly will, so it is a little surprising that the official smart lighting feature stops at 10. But it does.

Anyway, Core will allow you to set the dim level below 10%. Whether it will work or not will depend on the combination of bulbs, switch, and fixture.