This is the total byte count across all packets before payload compression is performed, used together with the post-compression byte count to compute the standard '1:x.xx' payload compression ratio. This raw byte count lets an admin verify the modem's payload compression engine, distinct from IP header compression, is actually shrinking application data, which matters most for compressible traffic like plain-text protocols versus already-compressed video. For example, 5,000,000 pre-compression bytes yielding a post-compression figure of 2,000,000 works out to a 1:2.5 compression ratio for that traffic sample.