Serial Monitor - Weird Symbol

When I used the "AT" commands, after I got a weird symbol and was wondering it means?

The symbol looks like this - ⸮

P.S. this is my first time using the forum, so if I am using the wrong thread please point me to correct thread

SerialMonitor_WeirdSymbol.png

SerialMonitor_WeirdSymbol.png

As you have not posted your sketch we cannot know what you are doing but at a guess you are trying to print a non printing character with a low ASCII value