Mine was fixed by a complete overhaul of the parent entry. Whoever composed the original one had a skewed view of primulas.
If you want some of the entries to have a different zone, you'll have to ask Dave to remove the zone 4 information from your parent entry. If it stays there, zone 4 will continue to be added to all of the entries even if they have another zone checked.
If you want all of them to say zone 4, then just leave that info in the parent entry and delete the other zone in the entries with two zones checked. You can find them by using the "Search by characteristics" feature.