Welcome to the forum @Bart80.2
The TEST command says what a sample is (it’s not one file – it’s one each of three types).
Backup Test block selection logic describes the detailed method by which files are chosen.
You can look at the size of your different backup files. The default size of a dblock is 50 MB.
There’s a smaller dindex for each dblock, and the dlist file size varies with backup file count.
One question is – what does it mean to test 10 percent of the backup? One view might say
that it means testing 10 percent of the dblock files, and because it’s a set, some other ones.
That would be the sample set count. To compute it roughly, take total file count * percent / 2.
The divide-by-two is because of dindex for every dblock. The question is – did code divide?
Add backup-test-percentage in addition to backup-test-samples [$25] #3296 asked for a “percentage of your backup”, but what does that mean, given the sample set idea? I’m thinking code should divide by 2.
How about if you look at backend statistics and post your KnownFileCount and FilesDownloadedCount
on a backup that doesn’t also do a Compact (which would add downloads) to see how the math lands?