The largest cargo of grain to leave a Ukrainian port since last month's agreement has departed the port of Chornomorsk.
The bulk carrier Ocean Lion left Tuesday with nearly 65,000 tonnes of corn destined for South Korea.
A UN document obtained by CNN on Monday sets out technical details for the corridor through which merchant ships exporting agricultural products can travel.
The document reads: "As a vessel moves through the Maritime Humanitarian Corridor, it is additionally protected by a buffer zone. The size of the buffer zone is a 10 nautical mile circle around the vessel while moving through maritime humanitarian corridor."
"No military vessel, aircraft or UAVs will close to within 10 nautical miles of a merchant vessel transiting the Maritime Humanitarian Corridor, excluding territorial seas of Ukraine," it said.
The High Seas Transit Corridor itself is 111 nautical miles long and 3 nautical miles wide.
Some context: Russia and Ukraine reached an agreement in Turkey last month to resume Ukrainian grain exports from Black Sea ports, which was a global breakthrough amid the world food crisis sparked by the war.
Since the invasion in late February, the World Food Programme (WFP) estimates that 47 million people have moved into a stage of acute hunger as a consequence of the war, and Western officials have accused Russia of using food as a weapon during its invasion.