What it means:
This means that the Aimtell script has been added to your website twice. Most commonly happens either because:
1) You are Shopify and they installed app and added tracking code.
Shopify takes care of the entire installation process, so it already adds the tracking code for you. If you install on Shopify and then add the tracking code separately, it will be added twice.
2) You are a non-Shopify user who added the tracking code manually on your site but also added it via a tag manager (like Google Tag Manager)
How to fix:
All you will have to do is check to see if you have installed the tracking code twice.
If you have installed the tracking code twice, remove the extra tracking code.