The subsite-wide default set according to the following steps can be overridden on a page-specific basis through the dashboard's left column dialog for any page. All the prior versions are in the databases; this just tells CommonSpot how far back to go when building the list to be displayed in the Version History dialog.
Login and navigate to any page in your subsite (or sub-subsite).
Click on the Admin button in the full-width toolbar, and select "Subsite Administration...".
Scroll as needed and click on your subsite so that it is highlighted; then click the Next button.
In the left column, if necessary, click to expand the "Properties" section.
Click on "Version History."
Observe the commentary and the current value of the number of days prior versions are to be displayed in the Version History list.
Change the value as appropriate. At this time, the largest permitted value is 999.
Click on the "Save" button at the bottom of the lightbox.