The linked pages seem to list scores in statements like below. This is a horribly inaccurate way to list scores of entering students. The scores of entering students are not the same as the scores of admitted students. More often than not, they are quite different, particularly at colleges with lower yields. As you said, they also seem to be assuming math 75th + writing 75th = composite 75th, which can lead to slight differences from the actual composite 75th, as you mentioned. In this example it was 1560 vs 1570.