Number of posts appearing on Homepage

The number is for normal posts. Sticky posts are always shown, regardless of the setting.

You’ll need to touch base with your theme provider on that as those are some sort of featured post mechanism instead of the ‘blog page’ control you were trying to set.

Not sure what the difference is. What are sticky posts? and can I still reduce those to 3.

Making a post “sticky” means that it will “stick” to the top of the posts list on the front end. (You can have more than one, so all sticky posts will be shown first, before the actual posts of the list.)
You make a post sticky either in the editor sidebar or using Quick Edit in the Posts list.
If you have no sticky posts, then either the theme is adding something in (which it should not), or you have a plugin that is affecting the query.

Your theme comes up as Twenty Fourteen and there might be a plugin driving that section of your home page.

https://www.ads-software.com/plugins/latest-posts/

I am on Twenty Fourteen and I already have latest post plug in.

Think I have sorted it. I unfeatured the past post; so it appears in the sidebar with its image but doesn’t appear in the posts which is now reduced to 3.

Thanks for the suggestions.

Meant to say I untagged the post.