The USGS estimates for reserves vary from year to year, depending upon nickel price, and have definitely been over 10% some years (see 2014 ; 2015 ; 2016). 16% is the highest I see so far from USGS.
However, the most recent (2018) USGS estimate is zero.
The USGS adds a footnote to the "zero" estimate:
the leading producer reported zero reserves owing to recent
A more complete explanation is in the USGS article The Mineral Industry of New Caledonia 2014 Minerals Yearbook:
About one-third of the land surface of New Caledonia’s main island, Grande Terre, consists of massifs containing peridotite. The country’s nickel resources account for about 25% of the world’s total. As of 2014, about two-thirds of the mineralized zones were conceded to mine operators and one-half of them had been subject to indepth research. More than 1,700 mining titles were owned by approximately 50 holders. The nickel reserves in New Caledonia accounted for 15% of the world’s nickel reserves, and the mine output accounted for 7% of the world’s nickel production (SMSP Group, 2014, p. 10; Direction de l’Industrie, des Mines et de l’Energie de la Nouvelle-Calédonie, 2015d; Kuck, 2015).
In other worlds, just considering how much known nickel is there ("resources"), it is 25%, but considering how much could be mined without losing money ("reserves"), it was 15%.
So basically the nickel in the territory is more expensive to mine relative to other places. 25% of the nickel is there, but currently no economically mineable nickel is there.