This is a 64-bit counter tracking the number of GTP-U packets that have been decapsulated on this interface, meaning the outer GTP-U tunnel header was stripped to expose the original subscriber IP payload. Since MEC decapsulates mobile traffic offloaded at the network edge in order to route it locally rather than back through the mobile core, this counter shows how much traffic is being locally processed. For example, a steadily climbing hh3cMecIfStatsDecap confirms the MEC gateway is actively terminating tunnels and extracting subscriber IP traffic for edge handling.