It will not be an attempt to increase data
Possibly different photo formats replacing the original format rt it may be the system obtaining the latest photographs available. I don't use the photos as it takes up grid space and that it more important for me however when I did have photos showing, every year or two I deleted the contents of my photo folder and started again but it may be more appropriate in your case to look at the dates of the duplicate photos and delete the older photos.
Fortunately it only takes up some space and doesn't affect the display of photos.
Alan
