This read-only value, marked obsolete in favor of the newer rbnMemoryTable, reported the number of memory blocks in use for a given module, where a block is the amount of memory returned by a single call to the AOS memory allocation routine; the description notes it could be used to check for leaks by noting the value, performing and undoing an operation, and confirming the value returned to its starting point. Admins used it as an early memory-leak diagnostic before it was superseded by rbnMemoryBlocksInUse. A block count that failed to return to its original value after an operation was undone would have indicated a leak in that operation's code path.