The block size is really only a "request" by the client. The proxy will attempt to provide the blocksize requested if it is available. If no blocks are available equal to or greater than the blocksize requested, the proxy will provide the largest available. If a block is available with a larger blocksize, the proxy will split the block to create the size requested.
Client version 2.9103-509 or greater is required for blocksize configuration. Proxy version 347 or greater is required for support of larger blocksizes (greater than 1*2^32). The blocksize parameter is only suppported for RC5-72.
|
distributed.net Faq-O-Matic : 
I set my client to receive a certain blocksize, but I sometimes notice smaller blocksizes being retrieved.