There are two techniques for doing so, the first being the previously mentioned rule groups and rule-execution flows.
这方面的技术有两种，第一种是前面介绍的规则组和规则执行流。
The basic rule for this checksum is that each of the first nine digits is multiplied by its position (that is, the first digit times one, the second digit times two, and so on).
这个校验和的基本规则是前九位数的每一位乘上它的位置(即第一位数乘上1，第二位数乘上2，依次类推)。
Note, that first two intervals may not comply with this rule.
注意，最开始的两个重复学习间隔不一定遵守这个法则。
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