Newton Interpolation

Newton Interpolation

Please tell me mathematical calculations difference between
apache-commons-math Interpolation and Matlab Symbolic math Interpolation.
public static PolynomialFunctionNewtonForm newtonInterpolation(double[] x,
double[] y) {
DividedDifferenceInterpolator interpolator = new
DividedDifferenceInterpolator();
PolynomialFunctionNewtonForm polynomialFunctionNewtonForm =
interpolator.interpolate(x, y);
System.out.println(polynomialFunctionNewtonForm.value(39));
return polynomialFunctionNewtonForm;
}
output: 0.7749640587391018 "after round" 1
P := interpolate(xList, yList, X)
evalp(P,X=39)
output: 29 (this is correct)
How can I modify my java code to get correct answer?