You can select a SQL Server from the 'Backup Manager', like in the attached screenshot1.jpg. This will show you data from all the different databases on that selected SQL Server. My SQL Server is named "DESKTOP-QQFBMVL", for example
And then for the 'Source', select 'LiteSpeed', like in screenshot2.jpg. This is so only LiteSpeed-generated backups (not native backups) will be included.
And for the 'Report Type' like in screenshot3.jpg, select just "Backup" so that only backups are displayed.
And also you select 'Period' and choose whatever time period you are interested in seeing the numbers for, such as "Last Week", for example, in screenshot4.jpg.
The 'Back Up Size' column will show you the size for each of the different LiteSpeed-created backups done on that SQL Server for that time range. It doesn't give you any totals, however.