Why is the demo stacked on echart's line chart incorrect?

http://echarts.baidu.com/exam.

for example, the search engine data on Monday is 820, but it seems to have a scale of more than 1500

Jan.26,2022

stacking chart, whose value is an interval value. The current height minus the height of one.
by setting the value of series [I] .stack, you can switch to stack line or normal line

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