Cressi, Leonardo underwater dive computer. When I use it, the bottom time was so short for the second dive and 4th dive, I would following the NDL time up. I would have to go to 19 feet before it would not put me in deco. At 20 feet it will continue to reduce the time to deco, move up to 19 feet and you would have 99 minutes (max display reading). when you give it a 2 hour or more surface interval it is more like other computer.
If you look at some of the latest dive tables you can not stay at 20 feet forever any more.