Unity2d character velocity keeps changing, why?

Question

Unity

The character's RigidBody2D velocity.y changes from -3.949388e-09 to 3.949388e-09. Even when he's on the ground, I don't understand why. Removed Run() from FixedUpdate, everything became normal, only after the character lands it changes a couple of times, and goes back to 0. Code attached:

Code

using UnityEngine;
using System.Collections;

public class CharacterControllerScript : MonoBehaviour
{
    public float maxSpeed = 10f;
    public float maxJump = 50f;
    private bool isFacingRight = true;
    [SerializeField]
    private bool isGrounded;
    private Animator anim;
    private Rigidbody2D characterRigidBody;

  private void Start()
    {
        characterRigidBody = GetComponent<Rigidbody2D>();
        anim = GetComponent<Animator>();
    }
  
  private void FixedUpdate()
    {
        Run();
        Jump();
        CharacterFlyOrFall();

    }

    private void Run()
    {
        float move = Input.GetAxis("Horizontal");

        anim.SetFloat("xSpeed", Mathf.Abs(1));

            characterRigidBody.velocity = new Vector2(move * maxSpeed, characterRigidBody.velocity.y);

        if (move > 0 && !isFacingRight)
            FlipCharacter();
        else if (move < 0 && isFacingRight)
            FlipCharacter();
    }
    
    private void CharacterFlyOrFall()
    {
        if (!isGrounded)
        {
            anim.SetFloat("ySpeed", characterRigidBody.velocity.y);
        }
        else
        {
            anim.SetFloat("ySpeed", Mathf.Abs(0));
        }
    }

    private void Jump()
    {
        if (isGrounded && Input.GetKey(KeyCode.UpArrow))
        {
            characterRigidBody.AddForce(new Vector2(0,maxJump));
            isGrounded = false;
        }

    }
    private void FlipCharacter()
    {
        isFacingRight = !isFacingRight;
        Vector3 theScale = transform.localScale;
        theScale.x *= -1;
        transform.localScale = theScale;
    }

    private void OnCollisionEnter2D(Collision2D collision)
    {
        if (collision.gameObject.layer == LayerMask.NameToLayer("Ground"))
        {
            isGrounded = true;
        }
    }
}

By the way, if the code is feces, then tell me why and how it should be, I will be glad)

Answer 1

The value +-3.949388e-09 is very small. Typically, these artifacts occur due to operations on floats, and this is due to the bit representation and implementation of floats. If it does not affect the game mechanics - I would score.