What a speed test measures
A speed test tries to measure the capacity of your connection under controlled conditions using optimized nearby servers and multiple connections.
A fast speed test does not guarantee a fast download. The two measurements are related, but they are not the same thing.
A speed test tries to measure the capacity of your connection under controlled conditions using optimized nearby servers and multiple connections.
A real download reflects the full chain: the server you are using, the route between you and it, your Wi‑Fi or Ethernet setup, your device, and background traffic.
Use a realistic speed number based on actual downloads from a similar service, or use a slightly conservative wired speed-test result.