Few things are suspicious here. There was 8 minutes difference between those two bets. So you were sitting for 8 minutes to see that what the hacker do with your remaining balance! Have you asked support about it after the first mysterious bet? If anyone else has compromised your account then he/she would withdraw your balance without placing any bets.

However, I'm not going to disregard the fact of account compromise. It can happen, I have seen four reports from different user about another site where pretty same thing happened. Click here and read about one of those issue.

You can check it by yourself. Those bets were made on 3rd July, so download your bet archive file of July 3 from (https://stake.com/transactions/archive/). Then upload the file on (https://data.page/json/csv). It will allow you to show the ip of each placed bets.