My question was how do companies accurately measure head grade,...

My question was how do companies accurately measure head grade, my mistake was thinking you were answering my question.

They wrote in the announcement: 

"During July to October 2018 a limited trial mining program was undertaken at the Rose of Denmarkmine (RoD), with the intent of comparing diamond drill hole gold grade intersections, with minedface grades and against the final processed head grade and recovered grade."

They were not trying to find recovery rates they were looking for grade uplift.