I don’t know.
How did you arrive at the figure of 4266 for the number of classical problems? There are 78 pages with 50 each, plus a 79th page with 46 = 3946. This ignores hidden problems of course.
The latest classical problem has an ID of 40808 - this suggests there are over 40000 problems in the database, but not all will be real problems, some will not have been made public, some will be hidden etc etc. But that does seem an awful long way from the 6534 you calculate.