Mark.
I tried several times times to connect your link, but somehow I can`t get connected. "Beide maschinen 10 weniger " would mean 10 rpm lower I guess we never used that. Achtung would be the same as "stand by" on any engineroom telegraph meaning the engine crew should be ready for action, being mostly for starting up or maneuvering. On a submarine it could be ready for surfacing, diving, schnorchling, batterycharging etc. as well.
Tore