Sorry, Stephanie...I don't think I've been very clear..I even confused myself, so I called CAP. I was told that a thermometer should be somewhere in the refrigerator (whether it is the sensor probe bottle, or the daily thermometer bottle) that has an amount of liquid in it that is equal to the least amount of product you would place in the refrigerator. Example: 20 mls of RBCs in a syringe.....then you would need a thermometer in 20 mls of liquid (10% glycerol) to mimic that volume.