I do believe that they ask those that place in the top four at sub's if they plan to go to state. If there are only 3 out of a district then they fill the remaining slots with those that did not place in the top four from the district that they will face directly at state, ie. if district 1 had only three wrestlers in a weight class and they were facing district 4, they would invite the 5th place wrestler from sub-district 4 to participate at state. If district 3 was facing district 2 and the weight class was full then only the top four would be invited from each of the sub-districts. It is my belief that the only reason that there are byes at state is because those that were invited did not show. Not sure if this is the case but I do think so.