Stop-loss issue

Hello everyone,
I have just started trading as a amateur.
Today I bought 40 shares of Airtel. It was BO. I placed a stop-loss value at 330, however it did not execute and now I have a loss of 250 since the LTP went down to 327
Please throw some light on this issue

You should attach screenshot of Executed positions page. So that I can see whats the issue