Place the original text on the left of the => and the new text on the right.

gettext_minmax_quantities.php

function change_deposit_text( $translated ) {
    $text = array(
        'The minimum order quantity for %s is %s - please increase the quantity in your cart.' => 'Ahh man, For %s you need a total of %s to order',
    );
    $translated = str_ireplace(  array_keys($text),  $text,  $translated );
    return $translated;
}

add_filter( 'gettext', 'change_deposit_text', 20 );