Don't confuse the contracts. There are 3 separate customer...

Don't confuse the contracts.
There are 3 separate customer contracts that make up 45kt for 2016 and each contract tolerates minus 10% volume delivery. The last contract is 20kt plus or minus 10%, so deliverying 18kt is enough.
"Galaxy Resources Limited (ASX: GXY) (“Galaxy” or the “Company”) is pleased to announce that it has successfully completed 2016 offtake supply obligations (contracted at 15,000dmt plus/minus ten percent) for its second customer. The MV Blessing SW sailed for China on 1 March 2017, with 13,700dmt of lithium concentrate."