Zephyr for JIRA 测试燃尽图的执行率是如何计算的？

mehll1213

Zephyr的英文介绍是这么描述的：
This metric tracks the progress of a test cycle, providing valuable information regarding how many tests are still unexecuted, what the current rate of execution is (= number of tests executed / number of days since the test cycle commenced) and extrapolating to when the projected date of completion would be based on the current rate.

我的翻译是：
测试燃尽图跟踪测试周期的进展，向用户展示还有多少测试未执行，与当前执行率(当前执行率=已经被执行的测试/测试周期开始至今的天数)，并对根据当前的执行率预计完成日期。

当如图，显示的评价执行率是2.7，不知是如何计算而来