I saw in the source code of the page (http://seotowers.com/demo/creagestal/galleries-2-columns/) that you insert the images and some shortcodes in the content of this page, thats why there are some more images. Please delete all images and Quickgallery shortcodes in the content section. Then click the “Add Media” button above the editor, then choose “Uploaded to this page” in the dropdown field, then WordPress will show you only the images attached to this page, and exactly these are the images for the quickgallery. No you can delete the images you dont want to have in the slider / quickgallery. With the attachment slider on the homepage its the same issue, also this shortcode will display always the images of your quickgallery.