Just below the photo you will see the photo
name, when it was posted and size information on the photo itself.
There may be two or three sizes shown depending on the size of
the photo you uploaded. Yahoo groups automatically creates a thumbnail
and intermediate photo as necessary when the photo is uploaded.
Be sure to look at these sizes to determine
how much space is being consumed, you must add all 3 size together
to get total space used.
In this example it's 1KB plus 16KB
plus 35KB for a total of 52KB.