IT World's description is garbled. The device isn't a debt clock, it's just a calculator that has lots of digits in its display. (Well, really, it's a gimmick whose purpose is to make a political/economic point; but its actual function is that of a calculator.)
As this is probably based on the national debt clock [1] and as the functionality more resembles a clock then a calculator I can't really protest the description.
That seems short-sighted.