SQS Cost Calculation For Batch Requests

I am using SQS Batching using a java client(AmazonSQSBufferedAsyncClient) for sending messages to SQS. I am sending 10 messages in one batch, But SQS monitoring is showing the Number Of Messages Sent is 10. Same for Number Of Messages Received and Number Of Messages Deleted Metric(Showing 10 count, expecting 1).

Below is the code to create buffered client

final AmazonSQSAsync sqsAsync = new AmazonSQSAsyncClient(SQSConfig.getCreds());

        final QueueBufferConfig config = new QueueBufferConfig()
                .withMaxBatchOpenMs(10000)
                .withMaxBatchSize(10)
                .withMaxInflightReceiveBatches(2)
                .withMaxDoneReceiveBatches(15);

        config.setLongPoll(true);

        bufferedSqs = new AmazonSQSBufferedAsyncClient(sqsAsync, config);

Below is the code to send a message.

public void sendBufferMessageInBatch(String message, String messageGroupId) throws ExecutionException, InterruptedException {

        SendMessageBatchRequest sqsBatchRequest = new SendMessageBatchRequest();

        sqsBatchRequest.setQueueUrl(SQSConfig.endpoint);
        List<SendMessageBatchRequestEntry> entryList = Stream.iterate(1, i -> i < 11, i -> i + 1)
                .map(numb -> {
                    String sendMessage = message;
                    sendMessage = sendMessage + "_" + numb;
                    sendMessage = sendMessage + "_" + messageGroupId;
                    SendMessageBatchRequestEntry entry = new SendMessageBatchRequestEntry();
                    entry.setMessageBody(sendMessage);
                    entry.setId("id_" + numb);
                    printSendMessage(sendMessage);
                    return entry;
                })
                .collect(Collectors.toList());

        sqsBatchRequest.setEntries(entryList);
        Future<SendMessageBatchResult> sendBatchMessageFuture = SQSConfig.bufferedSqs.sendMessageBatchAsync(sqsBatchRequest);
//        sendBatchMessageFuture.get();
    }

Questions:

1. Why are Number Of Messages Sent metrics showing count 10 instead of count 1?
2. What is SQS database or storage to store messages?