In Russian, выгода (vygoda), "advantage" (our translation), is profit, what benefits whoever receives it, and it is the word of the calculation that the narrator attacks. It appears dozens of times in a single chapter, in which he asks who computed it with exactness and calls the most advantageous of all, one's own will, the omitted advantage, that which enters no list.
Where It Appears
Quotes
His own will, willful and free, his own caprice, however wild it may be, his fantasy, irritated at times even to madness: all of this is precisely that omitted advantage, the most advantageous of advantages, which fits into no classification and because of which all systems and theories shatter and go to the devil.