Applied in the very same operation that creates the VM, rather than cloning at the source's size and reconfiguring afterwards. Has the same meaning as the setting of the same name of the "Reconfigure CPU"/"Reconfigure Memory" steps. Leave blank to keep the source VM's (or template's) own value. Variables can be used.
When the "Require enough CPU cores"/"Require enough RAM"/"Require enough free RAM" options are in effect, automatic host selection compares candidate hosts against this value instead of the source's.
The cores per socket of the source are kept unless "Number Cores per Socket" is set too, and this number has to be a multiple of it, or vCenter will refuse the request.