If your related table has one record for each story then the sum function in the second table or a summary field in the first table can be used to total up the related records. This assumes that you can set up the following relationship, which may be over simplified, so don't hesitate to post back with a more complete description of your tables if it is:
Table1::Stories = Table 2::Stories (calling your upper example table 1 and the lower table 2.)
Then Sum ( Table 1::Area ) defined in table 1 will compute the total area of the matching records.
And a summary field computing that "total of" Area can be defined in Table 1. If you put that field on a layout or in a portal based on Table 2, it will compute the same totals.