I am surprised that Chambers may have blundered on this. When I was trying to verify using a calculator I was NOT getting 0.1284 of a litre. HOWEVER in my ancient 1988 edition of Chambers, the wording is exactly as given by Waugh2 but the number is given in error as 0.1284.
I can only assume that the setter has used the 1988 Edition along with its typo!