The oil producer cited the operational tolerance clause which can adjust loading volumes by typically plus or minus 5% for logistical reasons, the people said.
ADNOC exports the bulk of its crude to Asia and its grades include Murban, Umm Lulu, Das and Upper Zakum.
The cut comes as the Organization of the Petroleum Exporting Countries and their allies, a group known as OPEC+, started to trim output by 2 million barrels per day from November, aiming to shore up oil prices.
“The output cut has to be reflected in the market. And it makes sense that oil producers want to hold off selling at such oil prices,” a Singapore-based trader said.
Benchmark Brent crude and WTI prices tumbled to 11-month lows on Monday.
Spot premiums of Middle Eastern crude, Oman, Dubai and Murban, slid this month as market sentiment soured amid oversupply fears.
OPEC+ is due to hold a meeting in Vienna on Dec.4.
ADNOC does not comment on commercial matters.