diff --git a/pepper/__init__.py b/pepper/__init__.py
index e0ca2438..089a4993 100644
--- a/pepper/__init__.py
+++ b/pepper/__init__.py
@@ -79,9 +79,9 @@ class PepperPrediction(PredictedProperty):
         dist = stats.lognorm(s=sigma_ln, scale=np.exp(mu_ln))
 
         # Exact probabilities
-        p_green = dist.cdf(p)  # P(X < a)
-        p_yellow = dist.cdf(vp) - p_green  # P(a <= X <= b)
-        p_red = 1.0 - dist.cdf(vp)  # P(X > b)
+        p_green = dist.cdf(p)  # P(X < p) prob not persistent
+        p_yellow = 1.0 - dist.cdf(p)  # P (X > p) prob persistent
+        p_red = 1.0 - dist.cdf(vp)  # P(X > vp) prob very persistent
 
         # Plotting range
         q_low, q_high = dist.ppf(quantiles)