The size of the file stored on the server should be available via your FTP client, or if you prefer:
<job> → Show log → Remote, and click on a list command to find the file. Format will be like:
{“Name”:“duplicati-bd7d60337b230420f8dc94be78e0acf47.dblock.zip”,“LastAccess”:“2024-06-21T19:07:16.637831-04:00”,“LastModification”:“2024-06-20T17:16:33.7459731-04:00”,“Size”:677,“IsFolder”:false},
If file is far larger than the default 50 MB Remote volume size, see what size you chose and why.