Expected utility theory (Lottery notation)
$$
\left(\frac{2}{100} \cdot 1000 \oplus \frac{98}{100}\cdot 0\right)
$$
is the lottery where you get $1000$ with probability $2/100$ and $0$ with probability $98/100$.
The expression
$$
20 \sim \left(\frac{2}{100} \cdot 1000 \oplus \frac{98}{100}\cdot 0\right)
$$
usually says that the decision maker is indifferent (in terms of preferences) between taking the lottery and having $20$ for sure.