Hopefully you will get clarification from @garachen, but for myself, I should be able to explain where the edge comes from. Example (hypothetical):Add value how so? To a firm or to the market?
Robinhood traders can only start trading at 9am pre-market, but I ca trade from 4am using my broker. If I get positive news on stock which is popular with RH traders, I can start accumulating prior to 9am. I should see immediate pop at 9. If I make money on this trade, I know exactly why.