Your second scenario is correct Magna. It will execute the order 100,100,100 against the three 100 share quotes and then all 700 remaining will go against the reserve of MM1 assuming (obvioulsy) his reserve is at least 700 shares obviously. Again, with the zero second delay functionality, this would all happen withing about 2 seconds (Naz says allow .7 second for each execution due to "system requirements" or something like that.