To seek insights on how to improve heuristic algorithms, we investigate the differences between baseline and optimal MILP schedules are investigated through two metrics. The assignment difference, referring to the operation-to-module assignment, is calculated as the percentage of operations assigned to different modules between two schedules. The sequence difference is the normalized Levenshtein distances between two operation sequences of the same module from two schedules and averaged over all modules. We note that sequence difference is more sensitive than assignment difference, as operation sequences can change on modules without altering the operation-to-module assignment, but the reverse is not true.