I just ran into this issue and emailed the supplier about low og. He told me a bunch of reasons this could happen mostly at first saying human error on volumes I was insulted and then went into stratification which is explained above with the mixing of water topped off with. I never missed an OG...
I know this is an old thread and Im a newb here but...I built an app that takes photo in and gives SRM . It works good enough I think but I would like to get some other brewers opinions on it though. Like the other guy said there is some complicated trig going on with conversions and other...