We have the Respirtech Encourage system, but the manual doesn't say what these numbers mean. I really never looked at them. But, my guess is that 228:43:10 is the number of hours on the machine. My daughter has had her machine for about 7 years and that number shows 2484:16:31! My husband also has a vest machine that he received a few years after my daughter, and his shows 1504:44:34.