Hi there - it looks like you selected "Square Tiles" for your galleries.
When you choose a tiled gallery format, the widths of your images are automatically calculated by WordPress so that they adapt to the amount of horizontal space available in your theme. These widths overrides the thumbnail width set under Settings > Media.
In order to pick up the thumbnail dimensions that you've set under Settings > Media, you'd need to select the "Default" setting for each gallery, instead of one of the tiles variations.
I hope this clarifies how the gallery thumbnail sizing works. Just let me know if you need further help.