If you are serious, for your edification I provide the following theory. Not definitive, but plausible nevertheless. Your fridge is kept cold by two things; a compressor and a thermostat. The thermostat has a thermometer. When the thermometer goes below above a certain threshold the compressor cuts in and runs until the thermometer goes below that level.

Either

1. The compressor cools the area near the NB Spuds more than the area around the thermometer.

2. Some the cooling of the spuds was compounded by evaporation of water as eliza said.

3. The air circulation in your fridge is restricted.

4. It is cooled in your fridge than you think.

5. Your compressor is broke and runs too much/

6. your thermostat is broke and causes your compressor to run too much.

7. any combination or 2 or more of the above.

8. one of your neighbors froze your spuds in a deep freeze and put them back in your fridge.