Another question on analysis

While looking back on a game I noticed the analysis said my move was an inaccuracy which put me ( black ) at -5.56. The line under said the best move would have been -6.65. So I backed up, rep[aced the inaccuracy with the suggested move and the rating didn’t go to the -6.65 as expected but went to -5.33 which not only was less than what i thought it would be , but also less than the ” inaccuracy “. What am I missing?