Minimal project to outline matrix application in Unity.
The picture below shows two cubes with the corresponding applied matrices.
This shows that matrices are applied from right to left. The corollary is vectors are seen as columns.
Note: matrix components are accessed in row-major order, i.e. with Matrix4x4[row,column] and Matrix4x4.m<row><column>. Therefore, Matrix4x4.m03 is the X-Translate component.