6.4.

When processing a RANGE that is set to THISANDFUTURE for recurrences, the order in which components have been overridden must be used to define which instances are affected by THISANDFUTURE. For example, say an event has three instances A, B and C. If B is overridden with a component with a RANGE=THISANDFUTURE parameter, then both B and C will be affected by the change. However, if C were subsequently changed, the change to C would not incorporate the changes done in B. Alternatively, if C was overridden first, and then B overridden with THISANDFUTURE, then the changes in B would be incorporated into C. Note that this means that the overridden component for C is effectively not used.