`Query.startAfter(Double value)` returns one more document than expected.

### [READ] Step 1: Are you in the right place?

Issues filed here should be about bugs in __the code in this repository__.
If you have a general question, need help debugging, or fall into some
other category use one of these other channels:

* For general technical questions, post a question on [StackOverflow](http://stackoverflow.com/)
with the firebase tag.
* For general Firebase discussion, use the [firebase-talk](https://groups.google.com/forum/#!forum/firebase-talk)
google group.
* For help troubleshooting your application that does not fall under one
of the above categories, reach out to the personalized
[Firebase support channel](https://firebase.google.com/support/).

### [REQUIRED] Step 2: Describe your environment

* Android Studio version: Android Studio Artic Fox 2020.3.1 Patch 4
* Firebase Component: Database
* Component version: 29.0.4

### [REQUIRED] Step 3: Describe the problem

Querying the database using the `startAfter(double value)` API is not returning the correct amount of documents (specifically returning one more than it should).

#### Steps to reproduce:
1. Run `flutter create testProject`.
2. Update "lib/main.dart" with the code under the "Relevant Code" header & input your firebase options as described in the code comment.
3. Run flutter app on an android device, the logs will output:
```bash
{search: 3}
{search: 4}
{search: 5}
```
4. Run flutter app on an iOS device will produce the correct output:
```bash
{search: 4}
{search: 5}
```

The relevant android code where we call `startAfter` is [here](https://github.com/firebase/flutterfire/blob/master/packages/firebase_database/firebase_database/android/src/main/java/io/flutter/plugins/firebase/database/QueryBuilder.java#L130)

#### Relevant Code:

```dart
import 'dart:async';

import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_database/firebase_database.dart';
import 'package:flutter/material.dart';

import 'firebase_options.dart';

Future main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp(

options: FirebaseOptions(
//
),
);

runApp(
MaterialApp(
title: 'Flutter Database Example',
home: MyHomePage(),
),
);
}

class MyHomePage extends StatelessWidget {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Flutter Database Example'),
),
body: Column(
children: [
ElevatedButton(
onPressed: () async {
//CREATES 5 DOCUMENTS IN DATABASE
DatabaseReference _testsRef = FirebaseDatabase.instance.ref('tests');
await _testsRef.set({
'yo':{'search':2,},
'so':{'search':3,},
'to':{'search':4,},
'fu':{'search':1,},
'bo':{'search':5,},
});
// QUERY THAT SHOULD RETURN 2 DOCUMENTS IF STARTING AFTER 3 (THE THIRD DOCUMENT)
DataSnapshot response = await _testsRef.orderByChild('search').startAfter(3).get();

response.children.forEach((element) {
// PRINTS OUT THE DOCUMENTS RETURNED
print(element.value.toString());
});
},
child: const Text('Press me'),
),
],
),
);
}
}
```

Hopefully, this makes sense as a flutter implementation! It is very straight forward. In a nutshell;
1. Create 5 documents.
2. Use orderByChild(String path) & startAfter(Double value) to query documents, and note that the query returns one more document than expected.

Let me know if you need any further information.