Jacobi algorithm problem... could wikipedia be wrong?

I am working on a c implementation of the jacobi algorithm, using wikipedia as an example.
I was trying to follow along with the given example on the page;

Jacobi method - Wikipedia, the free encyclopedia

The starting matrix A = [2 3,5 7]

then the lower is said to be [0 0,-5 0] which makes sence except that the 5 is negative.
the same is for the upper.

the page on strictly lower and upper parts of a matrix says nothing about negating them. am i misunderstanding something?

Could wikipedia be wrong?

Of course! Its useful for quick scan research pointers but should not form the basis of it because of potentially not so 'correct' articles. Of course a lot of articles are very authorative, but seek alternatives if in doubt

I would use MATLAB or other equivalent software (one free alternative is "octave" for Linux). Download a Jacobi algorithm for this language, and try some input. You can add simple print statements to the MATLAB code that shows the values at each iteration, and compare each iteration with your own C algorithm.

And as mentioned, it is very possible Wikipedia is incorrect. For Jacobi or other math stuff, I would use a math website/reference instead.