Sounds like SSI. That one's money-based. SSDI goes by time put in working (a certain length of time and the word "quarters" comes to mind). I'm sure someone else will have a better response(!), but basically, there are 2 kinds of disability: SSI and SSDI. They have different criteria.

I know what you mean about the amounts though. Their monetary expectations (SSDI too) are one of the scariest aspects.