This read-only Unsigned32, in ms, indicates the processing latency introduced by DRE/LZ/PLZ during decoding of data coming from the WAN, comprising LZ decompression followed by signature lookup, disk I/O, and data fetch to recreate the original data, as a since-last-reset aggregate. An admin monitors this because decode latency directly adds to the perceived response time for traffic arriving from the WAN side, unlike encode latency which affects outbound traffic. A rising decode latency, especially the disk-I/O-heavy lookup component described, would lead an admin to check DRE cache disk performance or contention.