إِنَّ مَعَ الْعُسْرِ يُسْرًا
Indeed, with hardship comes ease. (الشرح: 6)
Al-ʿusr is definite, while yusran is indefinite. The construction may present hardship as a recognized difficulty and ease as a benefit whose specific form is not named. The same difference remains in the repeated verse; definiteness and indefiniteness thus contribute to the texture of the reassurance.
One should not derive an unqualified numerical claim of exactly two distinct eases from indefiniteness alone. Such an understanding appears in exegetical discussion, but the securely available rhetorical observations are emphasis, the indefinite expression of ease, and deliberate repetition.