The solution is based onto a polynomial approximation formula obtained from strain energy V minimization ('Options'->'Show formulae' in the menu to see).
For concentrated loads or loads distributed over a small area this method does not provide the local peak stresses that may be obtained by other means: care should be exercised, based onto supplemental analyses, when assessing plate strength in such cases.
When present, the button 'Data' will download the matrix of the coefficients (without dimensions) aij as defined in sheet's formulae. Note that it is up to the user to link the downloaded matrix to the input data: when you download it, the matrix corresponds to the data in the sheet as you view it.