Spawn prefabs upwards with a fixed gap

[Abraham0Titus]

I am making a simple ball game that moves left and right when it hits a wall. I want the game to be like an arcade type game where the ball is on a platform and it keeps jumping up. So I've written a code to spawn a list of prefabs randomly upwards with a fixed gap. Since this is an endless runner I want the bottom Prefabs to be destroyed and new one to be spawned on top of the previous one. But when a new prefab is being spawned sometimes the gap made on the y axis is off but a decimal point and the more you play the bigger the gap is until the ball can't make the jump to the next platform. Any Solutions??

`using System.Collections;
using System.Collections.Generic;
using Unity.VisualScripting;
using UnityEngine;

public class PlatformSpawner : MonoBehaviour
{
public GameObject[] prefabs;
private GameObject platform;
public float gap = 3f;
public int maxInstances = 20;

private int numInstances = 0;

public ArcadeMovement scoreCountScript;

private float spawnerPosition = 0f;
private float lastSpawnedPosition = 0f;

private GameObject newPrefab;

private void Start()
{
    spawnerPosition = transform.position.y;
}
void Update()
{
    float scoreCounter = scoreCountScript.scoreCount;

    Vector3 currentPosition = transform.position;
    Transform currentRotation = gameObject.transform;
    currentPosition.x = 0f;
    currentRotation.eulerAngles = new Vector3(currentRotation.eulerAngles.x, currentRotation.eulerAngles.y, 0f);
    transform.position = currentPosition;

    if (numInstances < maxInstances)
    {
        int index = 0;
        if (scoreCounter < 25)
        {
            index = Random.Range(0, 3);
        }

        else if (scoreCounter >= 25 && scoreCounter < 50)
        {
            index = Random.Range(0, 5);
        }

        else if (scoreCounter >= 50)
        {
            index = Random.Range(0, 7);
        }

        currentPosition = transform.position + new Vector3(0f, Mathf.RoundToInt(numInstances * gap), 0f);
        newPrefab = Instantiate(prefabs[index], currentPosition, Quaternion.identity);
        currentPosition += newPrefab.transform.position;
        numInstances++;
    }
}

private void OnTriggerEnter2D(Collider2D collision)
{
    if (collision.gameObject.name.StartsWith("Platform"))
    {
        Destroy(collision.gameObject);
        Debug.Log("Platform Destroyed");
        numInstances--;
    }
}

}`