Thread:SlyCooperFan1/@comment-1713909-20170820222459/@comment-4925476-20170821001139

These might help explain you Sly. Note the "gap" each 10 or so missions. I think the grouping also denotes a story arc change in JP version counterpart (i.e the last mission before first gap is Export's counterpart of Scylla and Charybdis, the first mission after the third gap is the beginning of the Ouroboros arc)

Also interesting fact that these bars also appears in the title screen (!)