A method and technique are provided for efficiently acknowledging transmitted information in a system that employs variable rate data transmission, and skips data block sequence numbers depending on the transmission rate used. An RBB field in an ACK/NACK message includes a starting sequence number, an indication of a sequence number step, and a bitmap. The starting sequence number indicates a first block in a series or sequence of transmitted blocks that are being acknowledged via the ACK/NACK message. The sequence number step indicates a minimum difference between sequence numbers of blocks in the sequence. Where the sequence is ordered, the sequence number step is a difference between the sequence numbers of adjacent or consecutive blocks in the series. The bitmap is configured so that each bit in the bitmap represents an acknowledgment of one of blocks in the series. The RBB field can also include multiple starting sequence numbers, and both a sequence number step and a length for each starting sequence number. Each set of starting sequence number, sequence number step and length indicates a subseries or subsequence of the series of transmitted blocks that is being acknowledged via the ACK/NACK message. The starting sequence number indicates a sequence number of a first block in the subsequence, the length indicates how many blocks are in the subsequence, and the sequence number step indicates a difference between sequence numbers of adjacent blocks in the subsequence.