Here, food stocks is defined in the source paper as a group of “92 products” used “to reconstruct 50 years of aggregated food reserves, expressed in caloric equivalent (kcal), at the regional and global scales.” (Laio et al. 2016)
This is a great reference in that it does more than just look at stocks of grain. It does it for the end of each year, which is a pretty favorable case. The stocks of food would be considerably less right before harvest in the northern hemisphere, I would estimate ~3 months of food instead of 6. Also, their number is assuming 2880 kcal per day per person, which is appropriate to account for waste, but would not account for edible food fed to animals. But I agree with your rationing vegan number of approximately seven months if the catastrophe happened at the end of the year (but about half that for the worst timing scenario).
This is a great reference in that it does more than just look at stocks of grain. It does it for the end of each year, which is a pretty favorable case. The stocks of food would be considerably less right before harvest in the northern hemisphere, I would estimate ~3 months of food instead of 6. Also, their number is assuming 2880 kcal per day per person, which is appropriate to account for waste, but would not account for edible food fed to animals. But I agree with your rationing vegan number of approximately seven months if the catastrophe happened at the end of the year (but about half that for the worst timing scenario).