diff --git a/gdsc-smlm-ij/src/main/java/uk/ac/sussex/gdsc/smlm/ij/plugins/ResidenceTimeAnalysis.java b/gdsc-smlm-ij/src/main/java/uk/ac/sussex/gdsc/smlm/ij/plugins/ResidenceTimeAnalysis.java
index 2dd72e9c5..1ce5adb71 100644
--- a/gdsc-smlm-ij/src/main/java/uk/ac/sussex/gdsc/smlm/ij/plugins/ResidenceTimeAnalysis.java
+++ b/gdsc-smlm-ij/src/main/java/uk/ac/sussex/gdsc/smlm/ij/plugins/ResidenceTimeAnalysis.java
@@ -1118,7 +1118,7 @@ private static void showQqPlot(double exposureTime, int[] counts, Model m, Windo
         lo = 0;
         hi = x.getDouble(index);
       } else if (index == x.size()) {
-        lo = x.getDouble(index);
+        lo = x.getDouble(index - 1);
         // The last point should correspond to ~99% of the distribution. For an exponential
         // if we double the value it should bracket the quantile.
         hi = lo * 2;