Check out example codes for "unity custom update". It will help you in understanding the concepts better.

Code Example 1

float StartingRate = 0.5f;
float UpdateRate = 0.3f;

void Start(){
	InvokeRepeating("CustomUpdate",StartRate, UpdateRate);
    //This will start in 0.5s and start repeating in 0.3f 
}
void CustomUpdate(){
	//Your code here
}

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