Codeigniter Pagination showing that I am on the last page - php

Question

So here is what I had before. If I'd go to ciblog/categories/posts/5/, it would take me to a page showing all posts with a category with the id of 5.
And here is what I want to do. I want to go to ciblog/categories/posts/5 and it would show be 5 posts lets say. Then when I go to ciblog/categories/posts/5/3 it would offset by 3 so now I have the next 3 posts.
Currently I have 4 posts, just for testing. If I directly through my url go to ciblog/categories/posts/5 it shows 3 posts, and if I go to ciblog/categories/posts/5/3 it shows my one other post, so the amount of posts I am getting is correct based on the url.
BUT at the bottom it always shows that I am on page 2. When I use F12 and look at the elements both my pagination links show ciblog/categories/posts/5
So its not adding on the number at the end
Here is what I have for the pagination for this page. I used print_r and everything in $config is correct.
public function posts($id, $offset=0){
$category = $this->category_model->get_category($id);
if(empty($category))
{
show_404();
}
$config['base_url'] = base_url().'categories/posts/'.$id;
$config['total_rows'] = $this->post_model->get_posts_by_category_count($id);
$config['per_page'] = 3;
$config['uri_segment'] = 3;
$config['attributes'] = array('class' => 'pagination-link');
$this->pagination->initialize($config);
$data['title'] = $category->name;
$data['posts'] = $this->post_model->get_posts_by_category($id,$config['per_page'],$offset);
$this->load->view('templates/header');
$this->load->view('posts/index', $data);
$this->load->view('templates/footer');
}
Routes:
$route['categories/posts/(:num)/(:num)'] = 'categories/posts/$1/$2';
Reference:
I have been following a tutorial here: https://www.youtube.com/watch?v=WoQTjJepDWM&index=8&list=PLillGF-RfqbaP_71rOyChhjeK1swokUIS
Code for this tutorial is here: https://github.com/bradtraversy/ciblog
I am now adding on to this. The only changes I have made are shown above

Answer 1

$config['base_url'] = base_url().'categories/posts/'. $id . '/' . $offset;
$config['uri_segment'] = 4;
Because your pagination depends on offset, not id of category, then you should let it find for the offset with uri_segment 4, and your base_url must send an offset variable to find the offset.