It might be for the kitchen, because some houses have seperate 15-20 amp fuses fo the kitchen e.g. fridge, freezer, washing machine-handy, because if the ring main blows, the fridge doesn't go off.
Try taking it out and seeing what goes off in your house-be careful though, you may want to turn off the main switch first, remove the fuse and switch back on again rather than just pulling it out.