I don't know if that column is very well documented. I didn't find anything on the MS site. In my copy of Inside SQL (Delaney), a few values are mentioned here and there, but I get the impression there are (perhaps many) others.
1 - Duplicate key
2- Unique ndex
4- Duplicate Row
16- Clustered Index
2048- Enforce Primary Key
4096- Enforece Unique Constraint
Like I said, I think there are other values besides that. Interesting that it looks like the values are powers of 2 (dunno of that holds for the missing values.)
Are these the kind of values you are seeing?
bperry