We're given a spreadsheet with a correlation matrix for four stocks.
Then there is a calculation for average correlation, but I don't know how it's derived.
$$=\left(\operatorname{Average}(C14:F17)-\frac 14\right)\times\frac{16}{10}$$
I want to extend this calculation to six stocks. Can someone explain or point me to an explanation for how average correlations are calculated rather than some arbitrary scaling factors?