Its going to depend upon the concentration of Aprolium in the solution you have, and its VERY small - how small depends of course on how concentrated. This is a case for quite accurate measurements.
and as Townchicks says above, if your birds haven't been exposed, it will provide no benefit.
My preference (understanding, I have not had a case of severe coccidia outbreak on my grounds) is to raise my chicks in a brooder box till 7-10 days, provide them limited access to grounds over the next two weeks in areas where individuals of the main flock occasionally wanders thru but do not remain, i.e. the "wrong" ide of the elctric fence), then I move them out to the grow out pen where they are surrounded by - but not (mostly*) in contact with - the adult flock until about 8-9 weeks of age.
That helps expose them to the local parasites in a controlled fashion.
* a few of my hens would scale 6' of poultry wire to get into the grow out run and steal the babies' feed. The new electric fencing has (almost entirely) stopped that.
Further caveat - SOME of the feed (the layer mix) I get from the local mill which I use in my mix for my adult birds has amprolium. Sometimes all of it does. You take what you can get.