I could imagine that as a yearly food cost (a little under ~100/week). I lived off less than that when I was a grad student. It involved very little eating out (which this calculator accounts for) and consuming mostly stews or curries.

The food portion is likely quite off for very high cost of living areas. It uses the national average and applies an adjustment factor based on 4 regions: East (1.08), Midwest (0.95), South (0.93), and West (1.11). So, every area within said region has the exact same food costs.

Either that, or food costs really are similar within a region if you cook your own food and shop frugally.