good to know!
no idea why you'd see 50 then 28.
you can set Amount Of Items To Spawn to 50 and it will spawn 50 items. this will show 50 items in the server console window. in-game however, the status UI will show what is required to complete the event only. which is often less than the amount that was spawned because items can move into other containers like BBQ, TC, Fridge, Oven's and Lockers. any containers which are not required to complete the event will not be included in the status UI.
items which move into the tool cupboard are allowed to stack as well. so that would skew the number shown.