+/- before the Memory Clock value indicates an offset memory clock. If it is simply the number, it indicates a locked memory clock.
Command Line Launch String:
Replace [Wallet] with your wallet address and [Worker] with your worker name
nbminer.exe -a ergo -o stratum+tcp://ergo-us-west1.nanopool.org:11111 -u [Wallet].[Worker] -api 0.0.0.0:9999 -mclock -500 -cclock @570