Estimating Size of Extents

In working with Infor's (Nxtrend) warehouse application TWL, I have recently purged 8 years of data out for its End_of_Day process. Now I need to do a dump/load and specify a new structure *.st file. The new structure file will have a lot less extents defined in it, but I can't find anything a how to calculate what it should be. Is there a formula or method I can use to recalcuate how many extents I'll need? I'm running TWL 3.2 (with SX.e 3.2) from Infor on Progress 9.1D on a Unix AIX box.
 
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