The interval can be set at whatever you want.
But the display must be reset manually.
The 'maintenance' warning comes on at the set interval, after it was last reset - so if the interval's 3000 miles and it was last reset at 6,100 miles, it'll come on again at 9,100 miles
If you service before the light comes on, you can still reset it and it won't come on again till the next interval.
The handbook tells you how