What you posted is the irrelevant part. Many other parts of it are relevant to understanding how these chelators work. The part about the percentages removed are relevant to the efficiency of the chelators and how strongly they bind to mercury.

ALA can be used alone, yes, but it does not excrete mercury from the body as efficiently as DMSA so it is good to take the two together if possible, as it could reduce the number of rounds until you recover.