Have I defined a Composition relationship correctly?

I am trying to understand the difference between Composition and Aggregation a little better. I have read many questions on here like this one: http://ift.tt/2zRKbD2

Say a Customer is allocated offers when they register with a website.. Please see the code below:

public class Customer
    {
    public Guid id {get; set; }
    public string name {get; set; }
    public DateTime DateOfBirth {get; set; }
    public List<Offer> Offers {get; set; }

   public void GetOffers(List<Offer> AllOffers)
   {
     //Loop through AllOffers and assign the offers the person
     //is entitled to based on Age etc
   }

}

In the example above I use composition. Alternatively I could do this (Aggregation):

public class Customer
        {
        public Guid id {get; set; }
        public string name {get; set; }
        public DateTime DateOfBirth {get; set; }

       public List<Offer> GetOffers(List<Offer> AllOffers, List<Offer> MyOffers)
       {
         //Loop through AllOffers and assign the offers the person
         //is entitled to based on Age etc
       }    
    }

I believe I should be using composition (first example) because if a customer is deleted then the offers they are entitled to are deleted. Have I understood the difference between Aggregation and composition correctly? The reason I ask is because the Offer itself can link to many customers.