In my experience, it can take anywhere between 1 hour to 24 hours. It depends on the amount of data for that dimension (eVar, prop) that needs to be classified. (And probably whatever server load is happening at that moment in Adobe's environment.)
Generally, processing works in reverse chronology, i.e. newer data gets classified first, followed by older. Try narrowing your report date range to see if you get the expected classified data.
