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In the values for regionanchor and viewport anchor, the first percentage measures the x-dimension and the second percentage y-dimension from the top left corner of the region box. The table has these values swapped, e.g., 1 (top middle) regionanchor:0%,50% but top middle would be 50%,0%
Good catch. Fixed in https://dvcs.w3.org/hg/text-tracks/rev/e0010c7a20d7