[UMC] Announcement regarding share buyback amount reaching over 300 million TWD

1. Date on which the cumulative number of repurchased shares reached 2% of the total issued shares or the amount reached 300 million TWD: 2026/05/20 2. Number of shares repurchased this time: 10,020,000 3. Total amount of shares repurchased this time (TWD): 1,089,032,948 4. Average buyback price per share this time (TWD): 108.69 5. Cumulative number of company shares held within the buyback period: 30,551,000 6. Ratio of cumulative shares held to total issued shares within the buyback period (%): 0.24 7. Other matters to be stated: None