am i cooked (3A* offer)

i got an offer for cambridge bionatsci at christs today, of course im happy and proud but im also absolutely bricking it because the offer is for THREE A STARS??? im predicted 4 A stars, but realistically, any tiny thing going wrong could put me down to 2A*AA. is there a chance to still be accepted if i miss my offer narrowly? im going to try my best ofc but im so scared about having a bad day at a level and losing out on cambridge because i didn't 100% max my grades. ive seen some people say they can still accept you on lower grades but idk how common this is. ALSO WHY DID THEY DO THIS TO ME 💔 ive never seen such a high offer