cvx_cputime, not surprisingly, depends on MATLAB’s cputime command. It’s called once at cvx_begin and again at the end of cvx_end, and subtracted. Given that it’s pretty simple I can’t say for sure what’s going on. Perhaps cputime counts multiple cores twice—so for instance, perhaps it is saying that Gurobi consumed a total of 25 seconds spread across 4 CPU cores (6.25 seconds each).