Ah OK, I misunderstood , I thought this happened before immigration. I didn't realise you had reached immigration desk and handed over your passport. I thought it was a kind of pre-check before reaching the immigration desks.
I totally agree , if they were to put a definitive amount of days allowed in a certain amount of time on visa exempt it would be clearer . Everyone would know where they stand , even the I.O'S . It would also save them additional work because less people would attempt to break or bend the rules. If someone attempted to break the rules they deserve to be denied .