The computer will count down depending on your driving style, as early as 3,500 miles and as long as 10,000 miles. Most go off at around 7,500 - 9,000 miles based on average driving styles.
It's up to you on how you follow this, many do it earlier, at say 5,000 miles regardless of what the monitor says. Either way, if you want to stay in your factory powertrain warranty of 5yr/60K, you need to do an oil change at least once a year, regardless of how much time the monitor says you have to go.
So essentially, if you don't drive a lot, say less than 5,000 miles a year, do the oil change annually. If you drive 12,000 miles a year, bring it in every 6 months to be conservative, unless you drive really severe conditions and the monitor will require you to bring it in more often than that.
