I have a food production question. My current food production is at 120K per hour, my food consumption..

I have a food production question. My current food production is at 120K per hour, my food consumption is at 111K per hour, my truck is level 18, so when my food storage is below 600k, no food is being consumed. However, I've been noticing that when I log off with low food level, say 30K, after I log back on, my food level goes up to 39K, as if my troops are consuming food. Is this a bug and there's something wrong with my game, or is this intended behavior? Thanks.