Duty limits are based on numerous things. What time did you show for the trip that day (day vs night limits), are you reserve, trade, PDO, Draft, etc.
Then there are the "scheduled" limits vs "operational" limits. They can't go to 16 hrs just for you unless they declare an operational emerg., or you voluntarily extend up to 16. Usually, your operational limit will be your cap. This is only for domestic. Intl., get out your grid pending landings and block hours per period.