Misunderstanding Delay Signal from S-function

I am learning about S-function and try with an example exercise.

And I got a delay in result.

I really do not understand why the scope got DELAY in plots. P/S : I use file sfundsc1.m for S-Function ( you can search in default files of installed Matlab) and I believe that it is not any code about DELAY. So , I think my problem is in S-function using. Anyone can Help me.