If you make other deposits on the same account(/deposit address), a new entry is created. Subsequent deposits are not anymore merged all together. Every deposit has it's own life / activity. When a deposit gets fully rewarded, it becomes inactive.

This is useful to calculate the borrowed hash rate according to deposits:

Without this feature, if you deposited 1000 BTC, and your rewards was completed, if you added a 10 BTC deposit later, you would have 1010 BTC of infrastructure working until you get fully rewarded again. Now you would get 1000 BTC hashrate for the time that there is only the first deposit active, 1010 BTC hashrate when both deposits are active and 10 BTC hashrate when the first deposit is completed and the second is still active.