The 2nd and subsequent rounds are slightly different. You show both your BTC balances (as before) and your balance in bytes. You have a sort of basket that consists of a mixture of BTC and bytes. To determine the weight of the basket, every 62.5 MB are counted as 1 BTC. For example, if you have 125 MB and 3 BTC, the weight is 2+3=5 BTC. The distribution of new bytes on the 2nd and subsequent stages is proportional to the weight of your basket.
Does it mean that we have to lock the BTC balance in the linked address (for the first snapshot) for 3 months?
Put another way - My BTC balance in linked address at first SS is 3 BTC. after first SS, I move 3 BTC out and then move 6 BTC into linked address just before second SS. will the basket be counted as 2+6 = 8BTC? What is the weight if I have zero BTC in that linked address at time of second SS?