That pattern is in fact symmetrical. Note where it says bind off at the beginning of the next 2 rows. When you're at the beginning of the second row, your on the same end as the end of the first row. See what I mean?
Pattern instructions often give headers that describe the over-all section of what you're working on. "Shape Raglan" is telling you you'll be working the decrease area that is typcial of Raglans. It's like if they say "Shape Cap" for when you're going to work the top/cap of a sleeve.
Nice diagram, BTW!
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