howto/upgrades.md

@@ -40,10 +40,12 @@ different Debian releases:
  * jessie
  * stretch
  * buster (upgraded in 28 months)
- * bullseye (upgraded in 24 months and counting, running for 48 months
+ * bullseye (upgraded in 3 years and counting, running for 5 years
    and counting)
- * bookworm (running 1 month and counting)
+ * bookworm (running 18 month and counting)
 
+Note that the above X axis is inaccurate: it's scaled according to the
+number of samples, not to the *time* of the samples.
 </figcaption>
 </figure>