You can also go this way
$rows = get_field('repeater' ); // get all the rows
$specific_row = $rows[YOUR_ROW_NUMBER]; // 0 will get the first row, remember that the count starts at 0
$sub_field_value = $specific_row['SUB_FIELD_NAME']; // get the sub field value
This also explained on the tutorial page for repeaters https://www.advancedcustomfields.com/resources/repeater/
