// add a new participant to the system and calculate total players
Total_Savers=depositors.length+1;
depositors.length += 1;
depositors[depositors.length-1].etherAddress = msg.sender;
depositors[depositors.length-1].amount = amount;
I don't get why you add one and at the next line you subtract one.
edit: I got it, because adding the new depositor in the array would also increase depositors.length
Yes, the length must be integral, 1 spot hosts 1 value.
However the enumeration starts from 0 not 1.
So the first value is 0, the 2nd is 1, the 3rd is 2, and so on.
It's n-1.