Comment 3 for bug 1958027

The options refers to the width of the final pano, not of the individual images.
And this setting is only used by the assistant. Therefore it is at the correct position. (You can change the output size on the stitcher tab - as written in the help.)
The assistant calculates first the optimal width of the pano. Depending on the actual needed reprojections the canvas size can be bigger than the input images. If you think this is a bug please provide the pto file.
Then the width is reduced by the setting. The standard value of 70 % results in a pano which should be sufficient for most cases (Because of the Bayer pattern higher values don't result in higher resolution of the final pano. It increases only the processing time.)
The value refers to the width of pano - and not the size, which is completely different, e.g. reducing the width (and height) by 50 % results in the reduction of the image size to 25 %!