Allow a certain amount of duplicates in a Gravity From by field before kicking back a failure check.

custom_limit_gform_is_duplicate.php

<?php

add_filter( 'gform_is_duplicate', 'custom_gform_is_duplicate', 10, 4 );
function custom_gform_is_duplicate( $count, $form_id, $field, $value ){
  global $wpdb;
	$lead_detail_table_name = GFFormsModel::get_lead_details_table_name();
	$lead_table_name = GFFormsModel::get_lead_table_name();
	$sql_comparison = "ld.value=%s";

	switch(RGFormsModel::get_input_type($field)){
	    case "time" :
	        $value = sprintf("%02d:%02d %s", $value[0], $value[1], $value[2]);
	    break;
	    case "date" :
	        $value = GFFormsModel::prepare_date(rgar($field, "dateFormat"), $value);
	    break;
	    case "number" :
	        $value = GFCommon::clean_number($value, rgar($field, 'numberFormat'));
	    break;
	    case "phone" :
	        $value = str_replace(array(")", "(", "-", " "), array("", "", "", ""), $value);
	        $sql_comparison = 'replace(replace(replace(replace(ld.value, ")", ""), "(", ""), "-", ""), " ", "") = %s';
	    break;
	 }


	$inner_sql_template = " SELECT %s as input, ld.lead_id
	                        FROM $lead_detail_table_name ld
	                        INNER JOIN $lead_table_name l ON l.id = ld.lead_id
	                        WHERE l.form_id=%d AND ld.form_id=%d
	                        AND ld.field_number between %s AND %s
	                        AND status='active' AND {$sql_comparison}";

	$sql = "SELECT count(distinct input) as match_count FROM ( ";

	$input_count = 1;
	if(is_array($field["inputs"])){
	    $input_count = sizeof($field["inputs"]);
	    foreach($field["inputs"] as $input){
	        $union = empty($inner_sql) ? "" : " UNION ALL ";
	        $inner_sql .= $union . $wpdb->prepare($inner_sql_template, $input["id"], $form_id, $form_id, $input["id"] - 0.001, $input["id"] + 0.001, $value[$input["id"]]);
	    }
	}
	else{
	    $inner_sql = $wpdb->prepare($inner_sql_template, $field["id"], $form_id, $form_id, doubleval($field["id"]) - 0.001, doubleval($field["id"]) + 0.001, $value);
	}

	$sql .= $inner_sql . "
	        ) as count
	        GROUP BY lead_id
	        ORDER BY match_count DESC";

	$count = apply_filters("custom_limit_gform_is_duplicate_{$form_id}", apply_filters('custom_limit_gform_is_duplicate', count( $wpdb->get_col($sql) ), $form_id, $field, $value), $form_id, $field, $value);
	$input_count++; // CUSTOMIZE YOUR LIMIT (in this case 2 instead of 1)
	return $count != null && $count >= $input_count;
}