Grade confusion!

Okay I've probably posted about this before, so sorry if this is a repeat! I went into college today to see my English teacher about my A2 exam, and he was confused about the marks aswell, so thought it was worth asking on here. Basically the paper was out of 80, and I got 24, making that 30%. The marks on the front of the paper are in two columns, with 8 and 13 on the top row, and 21 and 13 on the second, with 24 written at the bottom where they're all added up. Now add those scored together gives 55. However, on my results slip it says I got 62 (out of 120, so UMS), which is 51%. I've looked at the actual answers, and on the second answer they've written 13 and band 2, so that must correspond to one of the numbers. Basically, could someone explain to me these numbers? I had hoped my teacher would be able to give me an explanation, but he's just as confused as I am!