What You See Isn't the Whole Truth
A player's quality values aren't exactly accurate at first glance. What you see is an estimate with minor deviations — usually just a few percentage points, rarely more. This applies to ALL players, even your own! Only once you've fully scouted a player do you see the exact values. Until then, it's an informed impression, nothing more.
Starting Scouting
On every player profile you'll find a "Scout" button. Click it and your scouting department gets to work. In Stadium → Scouting you can see the progress of all ongoing analyses. Every day you get a bit further — how fast depends on your scouting department and its personnel.
More Precise With Every Day
The great thing about scouting: the further the progress, the more precise the displayed values become. There's no hard jump from "wrong" to "right" — you basically watch live as the values settle in. At 0 % you see the full deviation. At 50 % the deviation is only half as large. At 100 % you see the naked truth — and a green checkmark confirms it.
Scout players on the transfer market BEFORE you buy them! A seeming bargain can look completely different after scouting.
Team-Specific
Scouting is team-specific. If Team A has scouted a player, Team B still sees the imprecise values. If Team B buys the player, they have to scout them themselves. Even after a sale: the new owner starts at zero.
Upgrading the Scouting Department
Without a scouting department (Level 0) things go slowly. Each level accelerates progress, and every staff member in the department gives an extra boost. At maximum you can bring the daily progress rate to a high tempo — then a player is fully analyzed in just a few days.