Graylog Memory/Heap usage

For memory usage ~780MiB:

services:
  elasticsearch:
    environment:
      - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
  graylog:
    environment:
      - "GRAYLOG_SERVER_JAVA_OPTS=-Xms768m -Xmx768m"

The JVM is using ???MiB of 729.6MiB heap space and will not attempt to use more than 729.6MiB