There doesn't need to be a difference in orders - I was just highlighting the unknown.

Even if everything is equal right down the line, same formation, orders, players etc....there will still be variation from one simulation to the other and 3% variation is a trifling amount.

In some matches I can start Normal attacking and gain a possession advantage then change to attacking and possession drops other matches it increases.

But one possible difference is he might have been pressing all over the park.....or not. ie his team is aggressively trying to regain possession in more areas than you. Counterattacking can produce possession stats that seem counter-intuitive depending on opposition orders.

But I'm just tip-tapping wereas in truth, the variation your seeing is so small that its easily explained as a random effect - you expected to roll a 3, 4,5 or 6 and got a 2.