...
OK done, https://github.com/ckolivas/cgminer/commit/6b62c402fa2939d7372764ce352e64aea78c71d0
It will be in 3.3.4 which is likely to be out today.
If you are curious, api.c has the calculations, search for "percent"
(and no, the devices do all use the same function, the 'Avalon' version which is correct for all the others also)