csv_header_change_filter_gettext.php

<?php //Do not include the opening PHP tag if you already have one

function csv_header_change_filter_gettext( $translated, $original, $domain ) {
 
    // This is an array of original strings
    // and what they should be replaced with
    $strings = array(
        'Count of this registration in the group registration ' => 'Count',
        'Registration\'s share of the transaction total' => 'SubTotal',
        'Transaction Amount Due' => 'Total',
        'Amount Paid' => 'Paid'
        // Add some more strings here
    );
    // See if the current string is in the $strings array
    // If so, replace its translation
    if ( isset( $strings[$original] ) ) {
        // This accomplishes the same thing as __()
        // but without running it through the filter again
        $translations = get_translations_for_domain( $domain );
        $translated = $translations->translate( $strings[$original] );
    }
 
    return $translated;
} 
add_filter( 'gettext', 'csv_header_change_filter_gettext', 10, 3 );