Why did an orange tick appear when logging in?

My 2011 series 13" MacBook Air has started to slow down of late and has developed an irritating and gradually worsening battery-life issue. I've always waited until about 5% remaining power before connecting the charger, and after finishing work last night it was no different. I rarely turn the Mac fully off just so I can access it instantly when needed - I've just disconnected the charger because the led was green and attempted to wake the laptop but it took longer than usual. Instead of a tap on the spacebar I had to hold down the power key until the screen lit and the log in window displayed. Next to my name was a small symbol displaying a white 'tick' in an orange circle, something I have never seen before. Can anyone clarify what this is? I'm unsure if it will cause further problems. I live in England but the Keyboard Layout is American so I'm not sure if it has something to do with an internal factory setting. Upon entering and confirming my password the symbol disappeared and I was able to use the device as normal.

As a subsequent result of the battery issues I've increased Time Machine back-ups from once every few months to once every two or so weeks, just in case. I'm performing the latest one now following the abnormality logging in.

All opinions are appreciated. Thanks!