This is the total byte count across all 'compressed' packets remaining after IP header compression has been performed, for this specific queue. Divided into the pre-compression byte count, it produces the header-compression ratio, cdmipHdrcompRatio, an admin uses to judge compression effectiveness for that queue's traffic type. For example, if post-compression bytes barely differ from pre-compression bytes for a given queue, that queue's traffic, likely large payloads relative to header size, simply isn't a good candidate for header compression.