The notation of a bar (vinculum, or overbar) over a whole number
doesn't seem to be very common. Here are some possibilities as to
what it could mean:
It is sometimes used as a grouping symbol, as in a fraction:
_____ __
3 + 1 x 5 = 20 so 67 = 67
I have also seen it used to refer to the average:
_ __
x = {1,2,6}, x = 3 so 67 = 67
(the average of one number is itself, of course).
I have also heard that it can be used to mean "1000 times whatever is
underneath", especially with Roman numerals - see the following Web
page, Final Answers by Gerard P. Michon:
