[Plugin: NextGEN Gallery] New images started a new page, but there was room!

I have a page that has 3 rows of 8 images across, so there are 24 spots for thumbnails. However the 3rd row has 4 empty spots available, so there are 20 images out of 24 spaces.

I added 2 images, but instead of adding them to the empty spots, it created a new page! Heres the result:
https://www.daviddmartin.com/?page_id=12

How can I force it to use the empty spaces?

https://www.ads-software.com/extend/plugins/nextgen-gallery/