Hello @Huynhthikieumy, 

I just wanted to inform you about the auction rules. Firstly, you must respect the end point. Respecting an end point means that you must make sure that the auction is fully complete before announcing the winner and completing the trade. Additionally, it also means applying the 15 minute rule. The 15 minute rule states: "All bids received within the last 15 minutes of the auction end point will further extend the auction a further 15 minutes". This will continue to apply until a full 15 minutes passes without any bids. I would also like to clarify that you cannot "add 5 minutes each time a bid is placed" .

In the case of this auction, both of these rules were not applied. I would advise reviewing the trade and auction rules so that you will avoid making any mistakes in the future. Please feel free to reach out if you have any questions. Have a great weekend!

Best Regards, 
Tandemaus