So, thank you so far.
"Were you just deleting one or two images, or an awful lot of them?"
- No, I was only deleting one picture, filename 2327.
"From what I can make of this, it appears that Recuva's overwriting file was created on top of another deleted file."
- I don't think so, because picture with filename 2256 wasn't deleted by me on windows neither with recuva, neither with camera. It is still on the sd-card.
I have researched on this toppic, perhaps recuva has the premium feature in it - that it is also able to overwritte slackspace / cluster tip area. This would be a positive thing and would make the secure erase more secure.
Thanks.
I have compessed the attachements to the demanded size.