Hey Chris,
Just spent over an hour talking with DAS support about this.
It's pretty much a bug.
The prices have a "pixel range" on the chart. So if you zoom in all the way, when you move your mouse up and down a bit on the chart the price will stay the same at 16.77 within a range. If you move your mouse to the lower range of those pixels (so it still shows 16.77 on the chart) it will give you 16.76 in the montage.
Unfortunately, as you zoom out to see more, it smashes the prices (and pixels) together; so you can't determine what pixel range you're in.... Sometimes it only gives you the upper pixel range and sometimes it only gives you the lower...
Unfortunately there is no solution. I'm still chatting with them... I'll let you know.