How to add 10 different css class to posts

Use the function post_class() in your template:

<div <?php post_class(); ?>>
// your post content
</div>

Then add a counter to the post classes per filter on post_class:

// functions.php
add_filter( 'post_class', function( Array $classes ) {

    static $number = 1;

    $classes[] = 'post-number-' . $number++;

    // reset the number
    if ( 11 === $number )
        $number = 1;

    return $classes;
});

You get a new class on each entry now that looks like post-number-1, post-number-2 and so on.