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add_filter( 'wpaesm_single_shift_cell', 'corne768709_show_clockin_clockout', 10, 4 );
function corne768709_show_clockin_clockout( $shift_text, $priority, $shift_id, $employee ) {

	$clock_times = 'Worked: ';

	$clockin = get_post_meta( $shift_id, '_wpaesm_clockin', true );
	if( '' !== $clockin ) {
		$clock_times .= $clockin;
	}

	$clockout = get_post_meta( $shift_id, '_wpaesm_clockout', true );
	if( '' !== $clockout ) {
		$clock_times .= ' - ' . $clockout;
	}

	return $shift_text . $clock_times;

}