clarify stats on the different releases

howto/upgrades.md

@@ -34,19 +34,20 @@ Some teams might be missing from the list.
 <img alt="graph showing the number of hosts per Debian release over time" src="/howto/upgrades/data.png" />
 <figcaption>
 The above graph shows the number of hosts running a particular version
-of Debian over time since data collection started in 2019, covering 5
-different Debian releases:
-
- * jessie
- * stretch
- * buster (upgraded in 28 months)
- * bullseye (upgraded in 3 years and counting, running for 5 years
-   and counting)
- * bookworm (running 18 month and counting)
-
+of Debian over time since data collection started in 2019.
 </figcaption>
 </figure>
 
+The above graph currently covers 5 different releases:
+
+| Suite    | Start      | End        | Upgrade time          | 3-release Overlap      |
+|----------|------------|------------|-----------------------|------------------------|
+| jessie   | N/A        | 2020-04-15 | N/A                   | N/A                    |
+| stretch  | N/A        | 2021-11-17 | 2 years (28 months)   | 3 months               |
+| buster   | 2019-08-15 | TBD        | 5 years and counting  | 18 months and counting |
+| bullseye | 2021-08-26 | TBD        | 3 years and counting  | 18 months and counting |
+| bookworm | 2023-04-08 | TBD        | 18 month and counting | 18 months and counting |
+
 # Minor upgrades
 
 ## Unattended upgrades