thanks for the suggestion.
The B2D in question has two .bkf files in it.
First, I tried to erase one of them ( approx 7MB ) - it grew to 53 MB on completion of the erase job.
Then I ran an overwrite test job backing up just one file to the same B2D. This ran to completion successfully but the .bkf remained the same size (although the used capacity is showing as the size of the file that we backed up.
My concern is that when I erase a file in any B2D, not just the one I describe above, it grows in size. Is there something you can suggest to find out why?
thanks