its because you've made the same page several times and named it the same thing. Everytime you create a new page and name it the same as something you already have, it will add a 1 or 2 or whatever at the end of the url.
You need to edit the SLUG and remove the dash and number from it, then press OK, then press update.
The slug may be the little url under your title in the page while editing it, or you may see below the textbox area a place that says "slug" where you can edit it there, if you don't see it, then go to screen options at top right corner of editor on that page and put a checkmark by "slug", then close the screen options, then you can see the slug.
Be sure to press OK, after editing the slug, then dont forget to press Update (republish the page) .. If you have any links hardcoded to the old links be sure to update those to your new page links.