Final answer:
When John deposits $100 into a fund, it means he is adding $100 to the total amount of money in the fund.
Step-by-step explanation:
When John deposits $100 into a fund at time t = 0, it means that he is adding $100 to the fund. This increases the total amount of money in the fund.
In terms of context, the question doesn't specify what the fund is for or what happens to the money after it is deposited. It could be a savings account, an investment fund, or a charity fund, among other possibilities.