Cleanup does not delete VCS changes in DB

Hi

We have cleanup setup to run every night and delete everything older than 30 days:
"Clean everything more than 30 days older than the last build"

However, I can see in VCS_CHANGES and VCS_HISTORY table a lot of much older data. What is the reason for that?
(VCS_CHANGES table currently holds 4GB in DB)

Thanks a lot