No such thing as too much caffeine. I forgot to ask: are your Bates
numbers *always* numeric, or might they have alpha characters?

By any chance do the clients have account numbers that are also
*always* numeric?

Is it possible that a client might have document numbers from 1 - 50,
60-75, and 1002-1009, for example?

Separating the start number and end number of a given range will likely
be helpful, but we don't have to decide that yet.