6. Acceptance or Rejection of Substitution Assignments
a. A pilot shall accept or reject a substitution assignment when offered.
b. However, when a pilot learns of a substitution offer through VIPS prior
to his initial availability period, he shall have up to 24 hours, or until 4
hours prior to to accept or reject the assignment, except that no
assignment may be rejected within 4 hours of showtime, whichever is
less, to call CRS and reject the trip. Failure to reject the assignment
in that time frame constitutes acceptance of the assignment.
This is how it should have changed to make it less confusing