Your ability lasts for a shorter time than it should. Note that this limitation cannot be applied to advantages with a “maintained” duration, such as Mind Control (though Mind Control with the Independent enhancement would qualify).
The limitation’s value depends on the reduction in duration:

Multiple Modifier Multiple Modifier
1/2 duration -5% 1/20 duration -25%
1/3 duration -10% 1/30 duration -30%
1/6 duration -15% 1/60 duration -35%
1/10 duration -20%

This table can be extended from the progression shown, but the minimum duration for an ability cannot be taken below one second. For example, Affliction (Disadvantage) has a variable duration that lasts a minimum of one minute, and is thus eligible for no more than Reduced Duration, 1/60, while unmodified Affliction has a minimum duration of one second, and could not take any level of Reduced Duration.