A Level fine art grade boundaries 2014

Hey! So i got a B in fine art AS level, with Bs in both units. I looked on the AQA grade boundary website and looked at the exact course i did (heres the website i used: http://filestore.aqa.org.uk/over/stat_pdf/AQA-A-LEVEL-GDE-BDY-JUNE-2014.PDF) to see how close to an A i was, and it says you need to get 70 in each of the first two units to get an A. I got 76 and 75 in the units which is why i dont understand why i got a B. There's probably a simple explanation, like I'm reading it wrong or something, but i DON'T UNDERSTAND. Someone please help!