ASOTrack shows conversion as downloads ÷ impressions over the selected period — the share of people who saw your app and installed it.
There’s no universal “good” number; it varies by category and traffic mix. What matters is the trend and how you compare with yourself after a change. Around 30%+ is treated as healthy in the ASO Health score.
Because it uses impressions as the denominator, conversion moves when your traffic mix changes, not only when your listing does. The “Why did this happen?” button breaks down which.