How it works
Everything you own is added up, everything you owe is subtracted, and what remains is your net worth. There is no modelling and no projection — it is a snapshot at the values you enter.
Cash and investments are reported separately from property, because the two behave very differently. A property cannot be sold in parts, so a position that looks comfortable in total can still be short of anything spendable.
More detail
The liabilities-to-assets ratio is shown alongside, since the same net worth can sit on very different amounts of borrowing.
Nothing is valued for you. The property figure in particular is your own estimate, and it is usually the largest and least certain number on the page.
To get the outstanding figure for your home loan rather than estimating it, use the loan balance calculator.