A2 Grading

Can someone tell if its true that if you want to get an A* in an A level subject you need a minimum 210 UMS from AS level and 270 UMS from A2? Like for eg if I get 495/600 is it an A? Or if I got 250 UMS in AS level and 260 UMS and I get 490/600 UMS will i get A? Because I got 260 UMS in A2 and that is below the minimum 270 or would it be an A.