The reason that you might be seeing the Peak traffic is higher than the max partition size was because partitions do not calculate and account for SYN packets, therefore if a large number of SYNs is seen for this class, it could cause a partition burst over its allowed limit.
However, if you would like for the SYN packets to be enforced by the partition size, you can issue the command " sys set tcpSynControl 1 ".
This is a system setting variable that basically enforces the SYNs to be included in the partition calculation and preventing the partition from bursting over it's configured limit.
An example as shown below:
PacketShaper# sys set tcpSynControl 1
Warning: This system command may impact the unit's operation.
Modifying its default value or setting should be done only
under the guidance of Packeteer Customer Support.
PacketShaper# sys set tcpSynControl
System values Current Default Min Max
=========================================================================
tcpSynControl 1 0 0 1
Warning: This system command may impact the unit's operation.
Modifying its default value or setting should be done only
under the guidance of Packeteer Customer Support.