How many cores does an intel i5-8400 processor have?

Question

Processors

I know that according to the documentation this processor has 6 cores. Windows shows the same amount. But one thing surprised me. One core is 100/6 ~ 16%. But I often notice that some processes that should be single-threaded load the processor by 25-26%. For example, opening a large document in Excel loads one core. There should be a processor load of 16%, well, or it would be clear 32% or a constantly floating percentage. But when the processor load fluctuates strictly within 25-26%, this suggests that I only have a 4-core processor.
How can such a situation be explained?
Now here's another option. I load a 3GB dataset into memory in Python. Single threaded task. CPU usage 24-26%.

Answer 1

Perhaps Windows thinks so for TurboBoost reasons.
The technology increases the power of one of the cores at the expense of idle others. Because the big question is how specifically the calculation of the processor load in Windows takes place.
I checked, in my Linux Mint, the load calculation follows your logic: if 2 threads are loaded, then it shows 25% in an 8-thread process.