Flutter – why my stateless widget can increase the value ?I'm using getx state management

When i study they said stateless widget can change value in short static value only display, but when i try to use getx in stateless it can change the value dynamic
getx.dart file and testingGetX.dart

`import 'package:get/get.dart';

class GetX{
RxInt number = 0.obs;
void increase() {
number = number + 1;
}
}`


`import 'package:flutter/material.dart';
import 'package:get/get.dart';
import 'package:get_api_2/getX.dart';

class TestingGetX extends StatelessWidget {
const TestingGetX({super.key});

@override
Widget build(BuildContext context) {
final authProvider c = Get.put(authProvider());
return Scaffold(
appBar: AppBar(),
body:Column(
  children: 
  [
    Text("value : ${c.number}"),

    Obx(()=>Text("value : ${c.number}")),
    TextButton(onPressed: () {
      c.number = c.number+1;
    }, child: Text("increase"))
  ]
),
);
}
}`