I found a quote from Stefan Werner:
“The window during rendering only shows the memory that the Cycles kernel itself allocated for rendering data. Depending on the settings, this may be system memory or VRAM.
This is by far not all the memory that Blender uses. Blender is further allocating memory for its data structures, for UI graphics, for geometry, etc. That is being tracked in the main Blender window.”
So, (if I understand it correctly) those numbers have little to do, with you running out of VRAM.
