The value "10" that you see in the Scope figure is actually the Simulation time of your model. To modify this, update the Simulation time in your diagram and the change will be reflected when you run the model.
You can also specify several time configuration properties in View>Configuration Properties>Time.
For more information about the Scope block, refer to the following link: https://www.mathworks.com/help/simulink/slref/scope.html
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