As with any module, this is also disabled by default.
Once enabled, by default a large number of revisions (99 to be specific) will be set to be on the safe side.
Changing this to say 5 will ensure that only the last or most recent 5 revisions will remain in the database and the rest automatically purged. This number is per post i.e., typically per Page and per Template. This can be changed to 0 as well.
For the revisions purging to happen for existing Pages and Templates, they need to be saved/updated either in the WP editor or in the Oxygen editor. Updating a Page/Template in the WP editor will not immediately reflect the updated number of revisions but can be seen after a page reload.
With new Pages/Templates created after enabling the module, revisions purging will be automatic per the set number.