Backups & restore points · Speed, progress and the first backup
How much space do Data Backup versions take up?
Short answer: Much less than a copy per version: after the first backup only changed pieces are stored, identical content is kept once, data is compressed, and older versions are thinned to daily, weekly and monthly.
Far less than a full copy per version. After the first backup, each version stores only the new and changed pieces, identical content is stored once no matter how many versions contain it, and backups are compressed.
To stop history growing forever, older versions are thinned over time: recent ones are kept in full, then one a day, then one a week, then one a month further back. See how long versions are kept.