OGR stubs are not of a fixed size. Some take a very long time, some are done in seconds. There is no way to select "long" stubs, or "short" stubs, and there is no telling what the stats server is going to distribute to you. You are always credited for the size of the stub you completed, and the amount of time to complete a stub is proportional to its size.
Leave your pproxy config alone. You probably got a bunch of really big stubs and you're likely to go back to averagely sized ones again soon.
I would call large stubs in the region of 300-400GNodes, small can be as small as <1GNode. Average is probably 75-125GNodes or so.
Does that clear things up, or make things worse?