I know that you can find the moment of inertia of a section using the section properties button, but I have a question on how they are calculated.

From my research the momnet of inertia can never be a negative number, however Ixy and Iyx are both negative numbers under the properties of a section I drew.  I think that this is related to the matrix math used to find the Ixy and Iyx, but I would like to know for certian.  Thank you in advance.