I don't think this is at all surprising. But by this do you mean you think dogs can count? It depends what you mean by 'count' I suppose. I doubt very much that dogs count things as humans do. I don't find it surprising they can remember 5 different things and fetch them. I also don't find it surprising that they can recognise a quantity. If I see three things, I know there are 3 without having to count them out 1, 2, 3...same with five etc. I should think dogs are quite good at this. But could you train a dog to count to 100? No, I doubt it. I bet their ability runs out when the quantities get too big to 'recognise'. I'm sure that if you fished around you'd find some studies or experiments though, I bet people have tried to test this.