The PRO-96 has ten banks of 50 channels each, for a total of 500 channels in its "working memory" (the memory/programming that's active when you're monitoring).
The scanner also has 10 "V-Scanner" folders, each of which holds a copy of the "working memory". (It has 11, if you count the "scratchpad" folder).
10 V-Scanner folders x 500 channels = 5000 channels, though only 500 can be active at any one time.