100 sale means MM needs shares 200 sale means MM needs shares bad-lot of orders he cannot cover 300 sale means MM is going to take price down to get shares 400 sale means trade sideways 500 sale gapping up or down depending on which way the sale went - this one can mean - let the stock find the PPS based on supply-demand, and it can mean hold the PPS at a given figure based on response.
some say this is hearsay, some say not.. Take it for what it's worth.