After several tests I find that if I eliminate just #24 I get the same result. However, if I eliminate two pictures and have only 22 pictures then the thumbnails work as advertised. A block centered above the "Description" box with the medium picture top left of that area, three pairs of two thumbs to the right and two rows of six and a final row of four below the medium pic that shows whatever thumbnail the mouse hovers over. It is interesting to note that there appears to be two empty spaces on the bottom row of thumbnails just waiting for me to add two more. But if I add even one, everything falls apart.
That said. Here is where the thumbnail pics are placed if I add the 23rd picture and choose TOP as the placement of the thumbs:
The "enlarged" pic is in the upper left corner (not centered as it should be) #1, 3, & 5 are vertical just to the left of the "enlarged" pic. Below the enlarged pic are two rows of five with my pics # 7 through 11 on row 1 and #13 through 17 on the second row. #2, 4, 6, 12 and 18 are way over on the right vertical and across from # 1, 3, 5, 11, and 17 but separated by 8 1/4 inches of nothing. #23 sits right on top of the "Description" heading. #19, 20, 21, and 22 are half way to the bottom of the description which happens to be pretty long so those pictures are 80 inches (not a typo) below the bottom row of the pics under the "enlarged" view box.
I tried all positions of the thumbs from the template choices. "Top" "Left" and "Top and Left" have absolutely the same results. "Right" and Top and Right" are equal to each other and cause a large horizontal mouse bar as it does not fit a screen. "Bottom" and "Top and Bottom" are equal to each other and everything matches similar to "Top" except that it all sits below the description and #23 sits on the "Payment" heading instead of the "Description" heading. The extra four are half way from there to the bottom of the page as the mouse scrolls. Not one of them showed a thumbnail for picture #24.
I really do not want to pare down my picture set to 22 from 24 but maybe that is what I will have to do.