I find the official docs quite scarce on this, so had to look from the wiki:
There the example is using only numbers.
We are trying to follow changes feed and download missing content on an embedded device. And right now it is hard to find a way to fill in the atts_since correctly. My first try was trying to fill in the current doc rev as string to it and I expected it to work - as now I effectively tell the server which is my newest version? (Maybe there is something about revision trees that I don’t get here? )