When we attended a local accepted students information session last year, they told us that Presidential Scholarship recipients are awarded both scholarships - the Chancellor's and the Presidential Scholarship -
C.U. Boulder Office of Financial Aid.
In other words, freshman/sophomore Presidential Scholarship recipients receive $10000 (P) + $5000 (C). In the junior and senior years, it goes down a bit, because the Chancellor's Scholarship is smaller - $10000 (P) and $2500 (C).
The Presidential Scholarships, however, go to an extremely small percentage of Chancellor's recipients - 1%, I believe.