Suppose a lamp is off. Perhaps its switch is open, its bulb failed, or the power supply stopped. The observation “the lamp is off” does not by itself entail “the switch is open.”
If a carefully restricted setup excludes the alternatives and establishes that, in those conditions, the lamp is off only when the switch is open, a warranted inferential premise becomes available.
Innī does not mean inferring one unique cause from any effect whatsoever. The inference must still be valid and its premises warranted.