Output details just after the ticket selector, this hook passes the Event ID ($EVT_ID) and the EE_Event ($event) for use within the function if needed

output_after_ticket_selector.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

//Output details just after the ticket selector, the function has the Event ID ($EVT_ID)
//and EE_Event object $event available for use.
function tw_output_details_after_the_ts( $EVT_ID, $event ) {

	echo "<h1>TESTING TESTING</h1>";

}
add_action( 'AHEE__ticket_selector_chart__template__after_ticket_selector', 'tw_output_details_after_the_ts', 10, 2 );