Memory usage spikes on shape key editing

Hi! I’m having a huge memory spike when editing a simple shape-key. My mesh has got multires modifier applied to it, but of course I’m editing the lowest one. After I finnish editing, memory doesn’t receed.
My system has 24 gb ram. I have 100 undo steps activated and 8000 mem limit in my Prefs > System.
Whta could be happening? Thx

If you are using gpu to render the memory limit is for gpu vram. As for shape keys it is a process heavy operation so can take more ram.