diff --git a/include/evalhyd/detail/probabilist/ranks.hpp b/include/evalhyd/detail/probabilist/ranks.hpp
index a594b8fac3edfe2089803c550bee0ceeec923104..376a80cc837b92cde453f99cac2424fad5df6a06 100644
--- a/include/evalhyd/detail/probabilist/ranks.hpp
+++ b/include/evalhyd/detail/probabilist/ranks.hpp
@@ -303,7 +303,9 @@ namespace evalhyd
                         auto l = xt::sum(t_msk_sampled, -1);
 
                         // compute the Delta score
-                        // $\bar{o_j} = \frac{1}{n} \sum_{k \in M_j} r_k$
+                        // \Delta = \sum_{k=1}^{N+1} (r_k - \frac{M}{N+1})^2
+                        // \Delta_o = \frac{MN}{N+1}
+                        // \delta = $\frac{\Delta}{\Delta_o}
                         xt::view(DS, xt::all(), xt::all(), m, e) =
                                 xt::nansum(
                                         xt::square(