Many items have special qualities. Some of these qualities are passive, always on, while others are active, which must be triggered by spending Advantage(s).
Active qualities require two Advantage to activate unless otherwise stated.
Source: EotE Page 155
For each level of this trait, add one Boost die to the attack dice pool.
Source: EotE Page 156
When using Auto-Fire, you must increase the Difficulty of the attack by one. If the attack hits, Auto-fire can be triggered by spending two Advantage. Each time it is triggered causes an additional hit to the target. Each hit does base damage + number of successes.
If you wish to hit multiple targets, this must be declared before making the check. Also, the initial target must be the one with the highest difficulty and defense