My MacBook has a dual-core processor with hyperthreading, so 4 software cores. Seems like the maximum CPU usage would be 400%? I missed the screenshot, but today
kernel_task shot up to 970% CPU for a split second. How is that possible?
Open Activity Monitor and go to the Window menu. One option under that menu is CPU Usage. Select that and a small window comes up and shows the CPU usage for each core. I think you have 8 cores but this menu item will answer that question.