Do not understand this code

Please, Im trying to set to 3, the number of displayed posts (Only) in homepage, while keeping 10 or more displayed posts in any of the other category pages, but I can not figure out how to do it with this code… Can you help?

<?php global $theme; get_header(); ?>

    <div id="main-main">

        <?php $theme->hook('main_before'); ?>

        <div id="content-index">

            <?php $theme->hook('content_before'); ?>

            <?php
                $is_post_wrap = 0;
                    if (have_posts()) : while (have_posts()) : the_post();

                    /**
                     * The default post formatting from the post.php template file will be used.
                     * If you want to customize the post formatting for your homepage:
                     *
                     *   - Create a new file: post-homepage.php
                     *   - Copy/Paste the content of post.php to post-homepage.php
                     *   - Edit and customize the post-homepage.php file for your needs.
                     *
                     * Learn more about the get_template_part() function: http://codex.wordpress.org/Function_Reference/get_template_part
                     */

                    $is_post_wrap++;
                        if($is_post_wrap == '1') {
                            ?><?php
                        }
                        get_template_part('post', 'homepage');

                        if($is_post_wrap == '2') {
                            $is_post_wrap = 0;
                            ?><?php
                        }

						if($is_post_wrap == '3') {
                            $is_post_wrap = 0;
                            ?><div class="post-wrap clearfix"><?php
                        }

                endwhile;

                else :
                    get_template_part('post', 'noresults');
                endif; 

                    if($is_post_wrap == '1') {
                        ?><?php
                    } 

                get_template_part('navigation');
            ?>

            <?php $theme->hook('content_after'); ?>

        </div><!-- #content -->
                    <!--
                     * Aqui deve colocarse o sidebar.
                     * Verificar index-original.php
                     -->
 <div class="entry clearfix">  </div>
    </div><!-- #main -->

<?php get_footer(); ?>