Easy question on percentage but different answers

GRE Quant Problem Solving
1

Kim has $100. I f her money were to decrease by 50 % every day, and she wants to acquire no more money, how many days would it take for her to fall below $5?

If we assume the 1st day to be $100 it would be 6 days. If it was a 0th day, then it would be 5th day. which one to choose?

2

We would choose it as 0th day.
Concept is, by the end of 1st day, it decreases by half.
So for that, our initial amount will be considered $100 (0th day)