Mycurvefit.com for regression not working

Question

I was testing some non linear Fit, so i entered the website Mycurvefit and used some sample data:

  Y    X   
 ---- ---- 
  10    7  
  20   13  
  30   17  
  40   23  

And Fitted with a Polynomial Cubic Regression and got this equation:

y = -5 + 1.633333*x - 0.05*x^2 + 0.0006666667*x^3

And curve:

But when i make y = -5 + 1.633333*x - 0.05*x^2 + 0.0006666667*x^3, x=7 the output is y=4 when x=7.

What am i doing wrong? Or is the website making some fitting regressions wrongly?

Thank you in advance,