Error when activated

I saw this too, and it is a warning about a potential conflict. It seems to be mostly harmless, but if you really want to get rid of it, then all you have to do is to modify the code inside custom-post-limits.php so that it has the parameter declaration i.e. $localized_heading_text = ” (never used in the extension of the class) for the input parameter as shown below…

/**
	 * Outputs the text above the setting form
	 *
	 * @return void (Text will be echoed.)
	 */
	public function options_page_description($localized_heading_text = '') {
		$options = $this->get_options();
		$current_limit = get_option( 'posts_per_page' );
		$option_url = '<a href="' . admin_url( 'options-reading.php' ) . '">' . __( 'here', $this->textdomain ) . '</a>';
		parent::options_page_description( __( 'Custom Post Limits Settings', $this->textdomain ) );
		echo '<p>' . __( 'By default, WordPress provides a single configuration setting to control how many posts should be listed on your blog.  This value applies for the front page listing, archive listings, author listings, category listings, tag listings, and search results.  <strong>Custom Post Limits</strong> allows you to override that value for each of those different sections.', $this->textdomain ) . '</p>';
		echo '<p>' . __( 'If the limit field is empty or 0 for a particular section type, then the default post limit will apply. If the value is set to -1, then there will be NO limit for that section (meaning ALL posts will be shown). For instance, you could set your Front Page to list 5 posts, but then list 10 on subsequent pages.', $this->textdomain ) . '</p>';
		echo '<p>' . __( 'All but the individual archive limits support a "paged (non first page)" sub-setting that allows a different limit to apply for that listing type when not viewing the first page of the listing  (i.e. when on page 2 or later).', $this->textdomain ) . '</p>';
		echo '<p>' . sprintf( __( 'The default post limit as set in your settings is <strong>%1$d</strong>.  You can change this value %2$s, which is labeled as <em>Blog pages show at most</em>', $this->textdomain ), $current_limit, $option_url ) . '</p>';
	}