If you add up the hourly totals from the SNINCR obs, you get 30". But there's a lot of fuzzy things going on. The depth starts at 3" yet when the snow picks up they report SNINCR 1/2 and an hour later SNINCR 2/5. So there's some weird math there.
BOX obviously didn't use the ASOS liquid total of 0.39" either. Those gauges were pretty terrible with snow back then...especially with wind.