Thanks for your question!
The reason we are given 8 Expert Advisors to trade is because they do not all trade at the same period of time. If they did all trade at during the same period of time we would not need 8 Expert Advisors as only 1 would do. For this reason we need to test the Expert Advisors to determine which of them are trading more profitable in the current market environment.
As an example, there are times when a certain Expert Advisor will be in a losing position for a several weeks or even several months while other Expert Advisors are profitable. It is therefore necessary for us to determine which Expert Advisors are currently being profitable.
Alan,