Yeah, I was wondering that too. Really, the two units have completely different functionality and feature sets, so it makes no sense to say that the 680 is 4x a DR-100.
I took it to mean that the preamps and possibly A/D sections of the 680 are pretty much the same as the DR100. Only at the very least that would mean the 680 is 3x the DR100 not 4x, as the 680 only has 6ch of analog inputs, the other 2ch are digital input only, and the DR100 doesn't have digital inputs.
Even trying to say the preamp/AD are the same on the two units doesn't really make sense either, as the max input for the DR100 is +2dbu on the XLR input and +6dbV on the 1/8" line input, whereas the 680 can take a +24dbu signal. If the 680 can take that much hotter a signal, something is different about it compared to the DR100.