basically when you book a 9 hour day at work to your time card, however the amount of hours you actually put in is no where close to 9 hours. for example you get in at 7.30am you have a 1 hour long lunch break from 12pm-1pm and you leave at 4pm. Thus working only 7.5 hours and getting paid for 9. Do this at your own risk - best time to do it is when managers/bosses have left and all snitches are not looking.
Careful though. DH-9's can be addictive and once you get away with 2 or 3 of them, you are more likely to take bigger risks and wanting to do them every day. you have to excercise self control only when doing them if 100% certain one will not get caught or ratted out.