Why does wrapping generate different results?

Question

Hi,
I have a tex box that I am using as a caption for an image. Both the image and caption are laid out in a column of text and both objects use text wrapping for some breathing room from the body text. I would like to create a tad more breathing room under the text box but when I add a pixel to the wrap buffer it causes the body text to move an entire line away. In other locations within the document performing the same action causes the body text to move away from the text box incrementally in direct correspondence with the added buffer values.
Why does increasing the wrap buffer sometimes cause the body text to jump an entire line away and sometimes just inch away one pixel at a time?
Thanks,
b

Answer 1

Thanks for the prompt reply.
I uploaded a .pdf that includes callouts to explain what I am asking.
If I understand what you are saying, the example I cite where the text moves one pixel at a time derives from the fact that the wrapped object is located at the top of the column, whereas when the text jumps an entire line it is because the wrapped object is below the first line of body text.Correct?
Is there a workaround you can think of? Split the text frames so the object is at the top of the column? modify the leading slug or baseline grid behaviors somehow?
http://www.seawead.org/wrap2.pdf
thanks again.
b