Microsoft have quickly responded to the 65,535 as 100,000 Excel 2007 bug. Their explanation is that it’s a “display only problem” with certain calculations that yield 65535 and 65536 results; the actual “in-memory” value continues to hold the correct figure. As such, the error will not propagate to other cells i.e a1=77.1*850 would display as 100,000, but b1=a1*2 would display (and hold internally) the correct result of 131,070.
However, it’s still a major bug, as Excel users act on the figures they see, not what’s behind the scenes and, contrary to what Microsoft says, it is possible to propagate the error to other cells if the affected cell is rendered using the round function i.e. a1=round(77.1*850,0) would again display as 100,000 but this time b1=a1*2 would result in the incorrect value (both displayed and in-memory) of 200,000.