page 7 says a colony needs 20kg of stores to see it through the winter.
Once again a simplistic view, or an unqualified statement. Just not quite true (as admiarably demonstrated in earlier posts by some).
Generally, I would think ten kilograms is probably nearer the mark for 'winter'.
Their value presumably includes the time from nil foraging (not even clustering?) in the autumn right through to expansion (brooding) in the spring and including a surplus (as zero stores is often fatal in the springtime when the colony is jam packed with brood - as there are no minus values allowed here!
They should have been more precise and said until 'a spring flow' or similar. More bees starve through lack of stores in the spring than during the winter. Stores for spring expansion (both pollen and honey) are arguably far more important than for those (three) winter months.
RAB