We upgraded our links from 3M to 6M and Packetshaper reports the sum of the link speed exceeds the interface NIC.
The error message is informing you that the WAN size exceeds the LAN size setting. For example, suppose you have the Inside and Outside ports set to 10Base-T Half-Duplex, which is 10 Mbps total for /Inbound and /Outbound. If your WAN setting is 12 Mbps (6 Mbps inbound and 6 Mbps outbound simultaneously), your WAN size has exceeded the LAN size setting.
You can change the LAN settings from 10Base-T half-duplex to 10BaseT full-duplex (or higher) if the two neighbor devices support these speeds.