8. A basketball team currently has a win rate of $40 \%$. If they win the next 10 games, their win rate will increase to $50 \%$. The team has already won $\qquad$ games.

将上面的文本翻译成英文，请保留源文本的换行和格式，直接输出翻译结果。 

Note: The last sentence is a repetition of the instruction and should not be included in the final translation. Here is the correct format:

8. A basketball team currently has a win rate of $40 \%$. If they win the next 10 games, their win rate will increase to $50 \%$. The team has already won $\qquad$ games.
$20$