Weird result with Matrix determinant

[Tugdual]

I wanted to calculate the determinant of the matrix
$$\begin{pmatrix} 1 & 0 & 2 & 8 \\ -2 & 1 & 1 & 5 \\ 6 & 3 & 5 & -4 \\ 10 & 4 & 3 & 0 \end{pmatrix}$$
Using Standard number format,
Prime Home says -647,000000002
Prime CAS says -647

Home is pretty close but what kind of algorithm can produce such a funny result to calculate a determinant with only integers?

Other question is: do we have an explanation for Floating and Rounded Number Formats? Those are recent additions not documented in the user guide.