Minimum trading days
The smallest number of days on which you must place at least one trade before a challenge phase can be passed.
If the minimum is four days and you hit the target on day two, you still need to trade on two more days, and every rule still applies on those days. Firms define a trading day differently, for example a day with at least one opened or closed trade.
Plan for it: on the extra days, small positions keep the target intact while meeting the rule. The minimum also sets a floor on how fast any challenge can finish.
Related
General definition. Rules differ between firms and change over time; your firm’s current terms always take precedence.