They're colored different here to indicate one new difference that you know about now, and that's that there is an orientation, there's an up and down on the chain.

这里被涂成不同的颜色,来表示另一个不同之处,它是有方向的,表示双链一条向上,一条向下

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So it's about 15 up and 15 down, then afterwards.

所以，大约是15分钟往上，15分钟往下，然后开始下一轮。

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