The dividend is calculated automatically, based upon your shareholder position for the month of September. That means that if you happened to, let's say, buy a lot of mineum at the end of September, it does not mean that your dividend payout for the month would be calculated based upon that number of mineum in your shareholder address. The dividend averages out what your position was over the entire month.
The dividend comes directly from mining activity which can be influenced by many different variables such as the number of GPU miners that are active, the profitability of mining over that time period, which mining algorithm was used. So the potential is there for your dividend to increase in size in the coming months.