My fridge starts calling for a restock as soon as it's down to 11/15. I mean, better too soon than too late, but it's keeping my staff busy. 😄
#Fridge restocked too early
halcyon rune
halcyon rune
11 doesn't seem to be a fixed value. Later in the game, the restock threshold went down to 7, and now it's back at 2, although I haven't touched the fridge (I moved other objects in the kitchen, but not the fridge). I can't say whether it went from 11 to 7 to 2 gradually or directly, I haven't paid much attention to this matter.
halcyon rune
I just had this issue again. I tried selling the fridges and buying new ones, but it didn't help. They still get restocked too early. But it didn't happen until I upgraded to the best fridge.
wary sapphire
Hi @halcyon rune! 
Thanks for your question! The specific fridge you're referring to is a meat combo fridge, meaning it contains both meat (5) and "regular" fridge items (10). Depending on which type of ingredient is consumed, the refill may take place at different levels. The supply warning will trigger when there's 1 or less remaining of any ingredient.
However, I agree this isn’t communicated very clearly in-game right now. I’ll make a note of it, and we may improve the messaging in a future update.