OK Let's see.... In the US we have E1 to E9, WO1 thru 4, and O1 thru O10 if you count 1 thru 4 star Generals as O7 thru O10 for a total of 23. Gree has 26 ranks so we would have to use our imagination and come with with just 3 more ranks that would be believable. An easy one is "Sergeant Major of the Army" for "E-10" and we could have a 5 star Generals Rank for "O-11" so that leaves just one missing. Got it! Commander in Chief.
OK Gree that took me about 30 seconds to come up with a ranking system that would be something close to authentic.
Geez, They should hire me as a military consultant.