As far as the database is concerned, there is not a version 8.7. They had version 8.0, then 8.1 ( 8i ), and then they moved onto 9i, which will be 9.x.

I would suggest that one of the two suggestions above is the answer : either it is a typo for 8.1.7, or the reference is to another Oracle product. The former seems most likely, as I don't think any of their other products is at anywhere close to v8, and they don't have any issues about keeping versions in line.