diff --git a/xcp_d/interfaces/utils.py b/xcp_d/interfaces/utils.py
index c89fa2c28..b2657c4f2 100644
--- a/xcp_d/interfaces/utils.py
+++ b/xcp_d/interfaces/utils.py
@@ -403,18 +403,18 @@ def _run_interface(self, runtime):
                 "LongName": "Number of Confounds",
                 "Description": (
                     "The number of confounds used in the denoising step. "
-                    "Combine this with num_dof_used_by_filter (+2) to estimate the degrees of "
-                    "freedom for bivariate correlations between censored, denoised time series "
-                    "(ignoring the effect of autocorrelation)."
+                    "To estimate the degrees of freedom for bivariate correlations between "
+                    "censored, denoised time series (ignoring the effect of autocorrelation), "
+                    "do num_retained_volumes - (num_confounds + num_dof_used_by_filter + 2)."
                 ),
             },
             "num_dof_used_by_filter": {
                 "LongName": "Number of Degrees of Freedom Lost by Temporal Filter",
                 "Description": (
                     "The degrees of freedom used up by the temporal filter. "
-                    "Combine this with num_confounds (+2) to estimate the degrees of freedom "
-                    "for bivariate correlations between censored, denoised time series "
-                    "(ignoring the effect of autocorrelation)."
+                    "To estimate the degrees of freedom for bivariate correlations between "
+                    "censored, denoised time series (ignoring the effect of autocorrelation), "
+                    "do num_retained_volumes - (num_confounds + num_dof_used_by_filter + 2)."
                 ),
             },
             "num_censored_volumes": {
@@ -428,7 +428,10 @@ def _run_interface(self, runtime):
                 "LongName": "Number of Retained Volumes",
                 "Description": (
                     "The number of volumes retained in the denoised dataset. "
-                    "This does not include dummy volumes or high-motion outliers."
+                    "This does not include dummy volumes or high-motion outliers. "
+                    "To estimate the degrees of freedom for bivariate correlations between "
+                    "censored, denoised time series (ignoring the effect of autocorrelation), "
+                    "do num_retained_volumes - (num_confounds + num_dof_used_by_filter + 2)."
                 ),
             },
             "fd_dvars_correlation_initial": {