topic been covered before try searching "maint light"
if it flashing and then goes away it is telling u need to service/ oil change soon. then if it just stays on it means 4runner due for service/ oil change then after service they will reset the maint light. but u are right it is a millage based reminder usually starts come on 1,000 miles be4 needs come into to be serviced then will stay on after the 1000 miles