your engine slows down to 700-800 r.p.m when the gear at the 4th and the speed of your car is at about 20-30km/hour. the data may be not exact, but almost.
so, it means that your engine is just at the free r.p.m (DAI4,SU4), no harm to it.
so, it means that your engine is just at the free r.p.m (DAI4,SU4), no harm to it.