Auto Transmission gear changes at which speed?

#1
My car Toyota Corolla Wagon - Petrol , EE104 (L)

It always shifts its gears up when it reaches 20kmh, 40kmh, and 60kmh only. So it needs to reach 60kmh to shift to the top gear which fuel efficient. Since i am driving in heavy traffic, my average speed is around 40kmh, so I have heavy fuel consumption. This gear changing pattern is a faulty?
 
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