Hi Jelena,
That is the tricky part, because the amount of space the detail section can have depends on the rest of the report sections and how much space they use up.
If they are template reports then you can figure out how much area is available by previewing in the Designer and then converting that area into Twips.
1440 twips = 1 inch.
So Maximum height is dependent on the amount of data you provide. Crystal will format the page accordingly and allocate as much data to the detail section that you provide.
Previewing in CR Designer with more than one page will give you the maximum number or rows you can use. Then you can do a count on the data provided to know if you will get one or more pages.
Don