The Current Value of an Investment is equal to the last Valuation (if it's automatically provided by Exirio), or the last Valuation manually inputted by you plus all deposits and minus all withdrawals since.
Let's take an example. If you bought a house in 2018 for 200,000 USD, valued it in 2019 at 250,000 USD then today's Current Value is 250,000. But if you did some renovation works in 2020 that you believe have increased its value by 25,000 USD (and therefore have accounted for it with a Deposit of 25,000 USD), the Current Value will be 275,000 USD.
Conversely, if you lent your cousin 50,000 USD two years ago and he has since given you back 10,000 USD (which you have accounted for with a Withdrawal of 10,000 USD), then Current Value will be equal to 40,000 USD.