The first oil change is at 5,000km
Viscosity is temperature dependent in multi grade oils. In climates where the temperature regularly soars above 40C, anything below sae 40 is under specification.
The specification in the service book gives the inner bracket of specification. Any oil on or beyond those brackets on BOTH sides is just fine. Having said that, broader range oils like 5w50 are more prone to sheering due to high dependence on VIs. A 10w40 would be just right for our climate for the corolla IMO.