Mean block in SIMULINK not behaving as expected

In a SIMULINK file, I used the mean block. I do not know how to interpret the results. Before adding the block, the signal's value is zero. After adding the mean block, the signal's value changes after one cycle as shown below:

Answer 1

[Pooya Taheri]

I had to change the time step. I assumed by choosing the default value (0), the model's time step will be inherited but I was wrong.