Depending on the content of the print data, the time from the start of printing in this app and print output may take some minutes.
Because mobile terminal OSes support multi-tasking, print processing continues for the enabled period (iOS 5.x/6.x: about 10 minutes, iOS 7.x: about 10 minutes) even if this app is not being displayed.
If the enabled period is exceeded, the job will be canceled.