Full backup question

tell me why the first full backup weighs 32 gigabytes, and the second full backup is already 500 megabytes?

11.12.19 14:53 No 31.97 GB
19.12.19 10:04 No 438.34 MB

UrBackup is very efficient on storage. The first backup must transfer the contents of every file selected. Subsequent full backups scan every selected file but only transfer files that have changed. It then creates a file structure that looks like a full backup from the bits it already has plus the new bits, giving a backup identical to what other products call a Full Backup without wasting time and storage keeping multiple copies of the same file. The incremental backup does the same, but relies on the Client component to identify the parts that have changed based on its record of what was already backed up.

Thank you!