Not sure what you’re doing here. “docker pull” is a docker function to request images from the server. It can’t run params.
--port-offset works okay like this.
docker run -it -p (...) dgraph alpha \
--lru_mb=<typically one-third the RAM> \
-zero=HOSTIPADDR:5080 --my=HOSTIPADDR:7080 \
--port-offset 2