what does @ mean at the end of a text message

It has no meaning by itself.

It was either part of something else that got truncated, misinterpreted, was a typo, or was part of a second text that followed.

Ask the sender. He might have meant to send something else. Some phones translate symbols differently than others. For example; send a heart, get a diamond.

Also

I dont know what the symbol on its own means but :@ means angry.