This is the Bonus Cache for the Glamis Adventure Lab Cache.
The container is located at N56 36.ABC W003 00.DEF and you will be able to collect five of these missing numbers as you do the Lab Cache.
The other missing number can be found by standing at the school car-park entrance and counting the number of chimney pots (not air-vents) on the school buildings' roofs. You should see XY chimney pots. The missing number = 3X + Y.
There is a small prize for FTF in the cache along with a variety of swap items.