Hi. you guys can try it too. its easy to reproduce. heres an example:

1-)I checked the FVD's folder in %firefoxprofile%>storage>default>%FVD's UUID%

Size : 992 KB.

2-) I add this page to dials.

Size : 1.13 MB

3-) I remove this page from dials. (Right click > delete dial >ok )

Size : 1.12 MB

Again (x2) :

I add this page to dials.

Size : 1.35 MB

Removed again.

Size : 1.29 MB

Again (x3) :

I add this page to dials.

Size : 1.52 MB

Removed : 1.51 MB

what i did was adding and removing 3 dials.

now i dont have any dials but FVD's storage occupies %55 more space.

maybe the extension doesnt delete thumbnails after captured them?