How do dates work in VK API statistics?

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Maybe someone came across a method for obtaining statistics from the VK API poll using the https://new.vk.com/dev/stats.get method where you can set the start and end dates.
For example, let's set an interval of 10 days from July 20 to July 30:
Statistics for 10 days
Now we will reduce the interval to 5 days from July 25 to July 30:
Statistics for 5 days
But we see exactly the same data.
And a question if date to not request the data for what period are returned? Last week, month?