Backups & restore points · When backups run
What does "Also make one version a day" do?
Short answer: It adds one scheduled version a day on top of As things change — a safety net for folders edited so constantly that a quiet moment to back up may never arrive. Turn it on in the set's Change… popover.
It adds a daily scheduled version on top of As things change. It's a safety net for folders you edit constantly: continuous backups wait for a quiet moment after your changes, and in a folder that never stops changing, that moment may never come.
Turn it on in the set's Change… popover, under As things change, then pick the time. The card's summary then reads something like "Backs up as things change · plus every day at 02:00".