If the DOJ estimate (which is always inflated, let's be real here) is $85M how could they have possibly made more than $123M on it? Unless you're talking about other hypothetical bribes that we don't know about.
You take that 85 Million and invest it (likely into growing a business unit but lets ignore that) and over 10 years it becomes greater than 85 million.
Otherwise though, McKinsey was awarded $209M in federal gov contracts in Canada over 12 years, so the numbers themselves don't seem relatively outrageous in terms of what McKinsey makes news for.