What is the default VFAT scratch partition size for ESXi 5.x when installed on a USB drive?

What is the default VFAT scratch partition size for ESXi 5.x when installed on a USB drive?

A.
600MB

B.
544MB

C.
4GB

D.
none

Explanation:
http://blogs.vmware.com/vsphere/2011/09/booting-esxi-off-usbsd.html(see bulleted # 3)