A gift schedule takes your overall zoo project funding target and breaks it down into manageable chunks.
It should allocate a high percentage of the donations required to a few big gifts, because all research shows that that is where most of your funding is going to come from.
It is there to concentrate the minds of all concerned that you really will need some serious contributions to make your goal. It militates against the dangerous contentions ‘every little helps’ ( …well, not much actually), or ‘if everyone gave’ ( everyone won’t, so someone is going to have to give big).
The gift schedule looks to stretch the generosity of your supporters a little, but it is also there as a courtesy to allow them to situate themselves at a level that is generous within their means. Some people will also go for the middle rank; a few will want to be right at the top.
It also acts as a kind of score card, so the campaign team can see where things are headed.
I attach a sample based on a small project I did a while back, with a relatively modest target, but caution that the arithmetic used will change according to the context
John