Reviews: max reviews per app (App Store max 500 per app and country). Search: results per keyword (up to 200). Charts: positions per chart (up to 200; App Store charts have 100). Minimums: 50 reviews per app, 30 search results per keyword and 50 chart positions; a smaller number is raised to the minimum, and those rows are collected and charged (e.g. 10 reviews asked = up to 50 collected, about $0.0045 per app). The run log warns about this at the start. Each request also has a small minimum ($0.0005 steps, minimum-top-up) that its results normally cover; it is only charged when a request delivers few or no results (e.g. an app with few reviews).
Minimum:1
Maximum:100000
Default:100