Help! Sequence Models Week 1

In this photo Prof. Andrew Ng said that X1=0 , X2=y1 , X3=y2 and so on and I didn’t understand , where’s our original sentence is inputted ? like for example where’s X that contain “hours” or when “hours” is entered to our model ?

At each point in time, we input the numerical representation of 1 word to predict the next word. Hope it’s now clear that the word hours will pass through the RNN after the word 15. We stop input to the RNN when <EOS> is reached.

Please go through the assignments and watch the lectures again.