As far as I know when a transaction is double spent, the first to be included in a block and start receiving confirmations is the going that is going to pass and the other one will be forgotten later on.
Any way, whoever sent you these coins is not trustworthy. He made this double-spent transaction to make you think you received the money. In fact he put lower fees on yours hoping that it won't get confirmed before his.
Thank you for explaining the effect. It looks like I need to talk to that person and ask him why he made this double-spent transaction.
Your Tx has got confirmation. So, the "Double Spend!" does not matter to u.
The thing is, the same coin i/p of your Tx was used in some other Tx, which is not yet confirmed.
Yes. Now I'm seeing it has received three confirmations so far. I guess this transaction can now be called a successful transaction. ViaBTC's acceleration really works! I appreciate your explanation.