There are 168 hours in a week (7 x 24). Thus 16.8 hours is a tenth of a week.
16.8 hours is 16 and 8/10 hours which is exactly 16 hours and 48 minutes.
As a night-shift worker myself, working in an industry (Security) which offers 24/7/365 services, I am aware that some 24 hour payment systems work on dividing up the week into sections and one way of doing that is to use tenths of a week.
We refer to some of our customers as a 'one-six-eight' customer or an 'eighty-four' customer depending on the number of the contracted hours involved. Then those contracted hours will be divided up to give shift rotations, which can result in fractions of an hour being allotted to individual shift-workers.
Microsoft Accounting :
This article describes how to enter fractions of an hour in time sheets in Microsoft Office Small Business Accounting, in Microsoft Office Accounting Professional, and in Microsoft Office Accounting Express.