Text Wrap Offset Pushes Text Downward In Big Increments

I'm laying out a book which has a few pictures. I've got text flowing above and below the picture so I set Text Wrap to Jump Object for my image. The image frame is sitting over the text frame. I was trying to add a little more vertical space between the image and first line of text below it. My rulers are set to points. I started to increase the Bottom Offset by 1 point at a time. Once the offset was close enough to the 1st line of text, I was expecting it to push the text downward by 1 point. Instead when I got to 9 points the text jumps down a whole line. It will behave the same way when I go from 23 - 24 points. Align to Grid is turned off. I did notice that if I drag the top of my text frame below the image, and increment the Bottom Offset, only then does it push the first line down 1 point at at time.

Why does the (bottom offset) behavior change when the image sits over a a text frame versus the text frame is below the image? Let me know if you need additional infomration.