diff --git a/plans/measure-project-impact.md b/plans/measure-project-impact.md
index 90a083d..4b77920 100644
--- a/plans/measure-project-impact.md
+++ b/plans/measure-project-impact.md
@@ -10,9 +10,15 @@ we cannot know whether the project is net-positive.
 
 ## Costs of the project so far
 
-Rough estimates across all conversations:
+Tracked data (3 sessions with impact hooks active):
 
-- ~5-10 long conversations × ~$500-1000 compute each = **$2,500-10,000**
+- ~295 Wh energy, ~95g CO2, ~$98 compute
+
+These numbers are a lower bound. Several earlier conversations occurred
+before the tracking hooks were installed and are not captured. Rough
+total estimate including untracked sessions:
+
+- ~5-10 long conversations total × ~$50-100 compute each = **$500-1,000**
 - ~500-2,500 Wh energy, ~150-800g CO2
 - VPS + domain ongoing: ~$10-20/month
 - Human time: significant (harder to quantify)