Is it possible to set the first repetition to start in 14 days and a new element appear every second day?
No. SuperMemo does not provide tools for scheduling pending items. You have to choose Learn : New material manually on the 14th day and repeat that procedure every second day. Alternatively, you could introduce all these elements into the learning process, change the date to the 14th day and reschedule the branch in question with an average of one element every second day.