Why is "Real Memory" greater than "Memory" for kernel_task process?
The kernel is special - it's the micro system that actually allocates memory and runs the virtual memory. You can just assume 3.60 GB is what your kernel has claimed and that 1.86 GB of that corresponds to what the task itself needs and the rest is the overhead / allocations to support all the demands made on the Mach kernel.

Every other line in Activity monitor behaves as one might expect, adding up fairly clearly once you ignore the kernel numbers:


Total virtual memory allocation is always the largest. Most of that is unallocated / not mapped physically and not in any category listed.
Real Mem is the non-shared and non-compressed allocation to that task.
Compressed Memory is the part of the total memory that has been compressed before being actively stored.
Private and Shared are both real memory usage but indicate if other processes might also need or be responsible for that allocation against the total.


For a larger discussion of the kernel_task, this question has some great links and discussion of how kernel_task is so very different than the rest of the processes you see on macOS.


What exactly does kernel_task do?